{"id":2134,"date":"2026-05-25T13:38:43","date_gmt":"2026-05-25T08:08:43","guid":{"rendered":"https:\/\/mymockmate.com\/notes\/?p=2134"},"modified":"2026-06-26T21:58:02","modified_gmt":"2026-06-26T16:28:02","slug":"ncert-class-9-maths-exercise-2-4-solutions-linear-growth-and-decay","status":"publish","type":"post","link":"https:\/\/mymockmate.com\/notes\/ncert-class-9-maths-exercise-2-4-solutions-linear-growth-and-decay\/","title":{"rendered":"NCERT Class 9 Maths Exercise 2.4 Solutions \u2013 Linear Growth and Decay"},"content":{"rendered":"<div class=\"mymoc-top mymoc-entity-placement\" id=\"mymoc-2054107151\"><div id=\"mymoc-650455696\"><a href=\"https:\/\/amzn.to\/4ehRB6n\" aria-label=\"printers\"><img src=\"https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/06\/printers.png\" alt=\"\" srcset=\"https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/06\/printers.png 1303w, https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/06\/printers-300x73.png 300w, https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/06\/printers-1024x250.png 1024w, https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/06\/printers-768x187.png 768w\" sizes=\"(max-width: 1303px) 100vw, 1303px\" width=\"1303\" height=\"318\"><\/a><\/div><\/div><div class=\"pdfprnt-buttons pdfprnt-buttons-post pdfprnt-top-bottom-right\"><a href=\"https:\/\/mymockmate.com\/notes\/wp-json\/wp\/v2\/posts\/2134?print=print\" class=\"pdfprnt-button pdfprnt-button-print\" target=\"_blank\"><img decoding=\"async\" src=\"https:\/\/mymockmate.com\/notes\/wp-content\/plugins\/pdf-print\/images\/print.png\" alt=\"image_print\" title=\"Print Content\"><span class=\"pdfprnt-button-title pdfprnt-button-print-title\">Print<\/span><\/a> <span class=\"pdfprnt-count-generation\">24<\/span><\/div>\n<hr class=\"wp-block-separator has-alpha-channel-opacity\">\n\n\n\n<h1 class=\"wp-block-heading\">Short Intro<\/h1>\n\n\n\n<p class=\"wp-block-paragraph\">Exercise 2.4 explains the concepts of <strong>linear growth<\/strong> and <strong>linear decay<\/strong> using real-life situations like plant growth, mobile depreciation, population increase, and prepaid balance reduction. These detailed step-by-step solutions help students understand linear functions and algebraic modelling easily.<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\">\n\n\n\n<h1 class=\"wp-block-heading\">Quick Information Box<\/h1>\n\n\n\n<figure class=\"wp-block-table\"><table class=\"has-fixed-layout\"><thead><tr><th>Topic<\/th><th>Details<\/th><\/tr><\/thead><tbody><tr><td>Chapter<\/td><td>Introduction to Linear Polynomials<\/td><\/tr><tr><td>Exercise<\/td><td>Exercise 2.4<\/td><\/tr><tr><td>Subject<\/td><td>Mathematics<\/td><\/tr><tr><td>Class<\/td><td>Grade 9<\/td><\/tr><tr><td>Main Concepts<\/td><td>Linear Growth &amp; Linear Decay<\/td><\/tr><tr><td>Difficulty Level<\/td><td>Moderate<\/td><\/tr><tr><td>Useful For<\/td><td>School Exams &amp; Olympiad Preparation<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\">\n\n\n\n<h1 class=\"wp-block-heading\">Concepts Used (Topics Covered)<\/h1>\n\n\n\n<ul class=\"wp-block-list\">\n<li>Linear Growth<\/li>\n\n\n\n<li>Linear Decay<\/li>\n\n\n\n<li>Linear Functions<\/li>\n\n\n\n<li>Algebraic Expressions<\/li>\n\n\n\n<li>Table of Values<\/li>\n\n\n\n<li>Depreciation<\/li>\n\n\n\n<li>Population Growth<\/li>\n\n\n\n<li>Balance Reduction<\/li>\n\n\n\n<li>Mathematical Modelling<\/li>\n<\/ul>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\">\n\n\n\n<h1 class=\"wp-block-heading\">Important Formulas<\/h1>\n\n\n\n<h2 class=\"wp-block-heading\">Linear Growth Formula<\/h2>\n\n\n\n<figure class=\"wp-block-image size-large\"><img fetchpriority=\"high\" decoding=\"async\" width=\"1024\" height=\"683\" src=\"https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-790-1024x683.png\" alt=\"\" class=\"wp-image-5570\" srcset=\"https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-790-1024x683.png 1024w, https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-790-300x200.png 300w, https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-790-768x512.png 768w, https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-790-1200x800.png 1200w, https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-790.png 1536w\" sizes=\"(max-width: 1024px) 100vw, 1024px\"><\/figure>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\">\n\n\n\n<h2 class=\"wp-block-heading\">Linear Decay Formula<\/h2>\n\n\n\n<figure class=\"wp-block-image size-large\"><img decoding=\"async\" width=\"1024\" height=\"683\" src=\"https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-791-1024x683.png\" alt=\"\" class=\"wp-image-5574\" srcset=\"https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-791-1024x683.png 1024w, https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-791-300x200.png 300w, https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-791-768x512.png 768w, https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-791-1200x800.png 1200w, https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-791.png 1536w\" sizes=\"(max-width: 1024px) 100vw, 1024px\"><\/figure>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\">\n\n\n\n<h2 class=\"wp-block-heading\">Depreciation Formula<\/h2>\n\n\n\n<figure class=\"wp-block-image size-large\"><img decoding=\"async\" width=\"1024\" height=\"683\" src=\"https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-792-1024x683.png\" alt=\"\" class=\"wp-image-5577\" srcset=\"https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-792-1024x683.png 1024w, https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-792-300x200.png 300w, https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-792-768x512.png 768w, https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-792-1200x800.png 1200w, https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-792.png 1536w\" sizes=\"(max-width: 1024px) 100vw, 1024px\"><\/figure>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\">\n\n\n\n<h2 class=\"wp-block-heading\">Population Growth Formula<\/h2>\n\n\n\n<figure class=\"wp-block-image size-large\"><img loading=\"lazy\" decoding=\"async\" width=\"1024\" height=\"683\" src=\"https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-793-1024x683.png\" alt=\"\" class=\"wp-image-5580\" srcset=\"https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-793-1024x683.png 1024w, https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-793-300x200.png 300w, https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-793-768x512.png 768w, https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-793-1200x800.png 1200w, https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-793.png 1536w\" sizes=\"(max-width: 1024px) 100vw, 1024px\"><\/figure>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\">\n\n\n\n<h1 class=\"wp-block-heading\">Questions &amp; Step-by-Step Solutions<\/h1>\n\n\n\n<h1 class=\"wp-block-heading\">Question 1<\/h1>\n\n\n\n<p class=\"wp-block-paragraph\">Suppose a plant has height 1.75 feet and it grows by 0.5 feet each month.<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\">\n\n\n\n<h2 class=\"wp-block-heading\">(i) Find the height after 7 months<\/h2>\n\n\n\n<h3 class=\"wp-block-heading\">Solution<\/h3>\n\n\n\n<figure class=\"wp-block-image size-large\"><img loading=\"lazy\" decoding=\"async\" width=\"1024\" height=\"768\" src=\"https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-775-1024x768.png\" alt=\"\" class=\"wp-image-5535\" srcset=\"https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-775-1024x768.png 1024w, https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-775-300x225.png 300w, https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-775-768x576.png 768w, https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-775.png 1448w\" sizes=\"(max-width: 1024px) 100vw, 1024px\"><\/figure>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\">\n\n\n\n<h2 class=\"wp-block-heading\">(ii) Make a table of values for t varying from 0 to 10 months and<br>show how the height, h, increases every month.<\/h2>\n\n\n\n<figure class=\"wp-block-image size-large\"><img loading=\"lazy\" decoding=\"async\" width=\"1024\" height=\"819\" src=\"https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-776-1024x819.png\" alt=\"\" class=\"wp-image-5537\" srcset=\"https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-776-1024x819.png 1024w, https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-776-300x240.png 300w, https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-776-768x615.png 768w, https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-776.png 1402w\" sizes=\"(max-width: 1024px) 100vw, 1024px\"><\/figure>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\">\n\n\n\n<h2 class=\"wp-block-heading\">(iii) Find an expression that relates v and t, and explain why it<br>represents linear growth.<\/h2>\n\n\n\n<figure class=\"wp-block-image size-large\"><img loading=\"lazy\" decoding=\"async\" width=\"1024\" height=\"683\" src=\"https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-777-1024x683.png\" alt=\"\" class=\"wp-image-5541\" srcset=\"https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-777-1024x683.png 1024w, https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-777-300x200.png 300w, https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-777-768x512.png 768w, https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-777-1200x800.png 1200w, https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-777.png 1536w\" sizes=\"(max-width: 1024px) 100vw, 1024px\"><\/figure>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\">\n\n\n\n<h1 class=\"wp-block-heading\">Question 2<\/h1>\n\n\n\n<p class=\"wp-block-paragraph\">A mobile phone is bought for &#8377;10,000. Its value decreases by &#8377;800 every year.<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\">\n\n\n\n<h2 class=\"wp-block-heading\">(i) Find the value of the phone after 3 years.<\/h2>\n\n\n\n<h3 class=\"wp-block-heading\">Solution<\/h3>\n\n\n\n<figure class=\"wp-block-image size-large\"><img loading=\"lazy\" decoding=\"async\" width=\"1024\" height=\"819\" src=\"https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-778-1024x819.png\" alt=\"\" class=\"wp-image-5544\" srcset=\"https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-778-1024x819.png 1024w, https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-778-300x240.png 300w, https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-778-768x615.png 768w, https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-778.png 1402w\" sizes=\"(max-width: 1024px) 100vw, 1024px\"><\/figure>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\">\n\n\n\n<h2 class=\"wp-block-heading\">(ii) Make a table of values for t varying from 0 to 8 years and<br>show how the value of the phone, v, depreciates with time.<\/h2>\n\n\n\n<figure class=\"wp-block-image size-large\"><img loading=\"lazy\" decoding=\"async\" width=\"1024\" height=\"683\" src=\"https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-779-1024x683.png\" alt=\"\" class=\"wp-image-5546\" srcset=\"https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-779-1024x683.png 1024w, https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-779-300x200.png 300w, https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-779-768x512.png 768w, https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-779-1200x800.png 1200w, https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-779.png 1536w\" sizes=\"(max-width: 1024px) 100vw, 1024px\"><\/figure>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\">\n\n\n\n<h2 class=\"wp-block-heading\">(iii) Find an expression that relates v and t, and explain why it represents linear decay.<\/h2>\n\n\n\n<figure class=\"wp-block-image size-large\"><img loading=\"lazy\" decoding=\"async\" width=\"1024\" height=\"683\" src=\"https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-780-1024x683.png\" alt=\"\" class=\"wp-image-5548\" srcset=\"https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-780-1024x683.png 1024w, https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-780-300x200.png 300w, https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-780-768x512.png 768w, https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-780-1200x800.png 1200w, https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-780.png 1536w\" sizes=\"(max-width: 1024px) 100vw, 1024px\"><\/figure>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\">\n\n\n\n<h1 class=\"wp-block-heading\">Question 3<\/h1>\n\n\n\n<p class=\"wp-block-paragraph\">The initial population of a village is 750. Every year, 50 people move from a nearby city to the village.<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\">\n\n\n\n<h2 class=\"wp-block-heading\">(i) Find the population of the village after 6 years.<\/h2>\n\n\n\n<h3 class=\"wp-block-heading\">Solution<\/h3>\n\n\n\n<figure class=\"wp-block-image size-large\"><img loading=\"lazy\" decoding=\"async\" width=\"1024\" height=\"768\" src=\"https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-781-1024x768.png\" alt=\"\" class=\"wp-image-5551\" srcset=\"https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-781-1024x768.png 1024w, https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-781-300x225.png 300w, https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-781-768x576.png 768w, https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-781.png 1448w\" sizes=\"(max-width: 1024px) 100vw, 1024px\"><\/figure>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\">\n\n\n\n<h2 class=\"wp-block-heading\">(ii) Make a table of values for t varying from 0 to 10 years and show how the population, P, increases every year.<\/h2>\n\n\n\n<figure class=\"wp-block-image size-large\"><img loading=\"lazy\" decoding=\"async\" width=\"1024\" height=\"683\" src=\"https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-782-1024x683.png\" alt=\"\" class=\"wp-image-5554\" srcset=\"https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-782-1024x683.png 1024w, https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-782-300x200.png 300w, https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-782-768x512.png 768w, https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-782-1200x800.png 1200w, https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-782.png 1536w\" sizes=\"(max-width: 1024px) 100vw, 1024px\"><\/figure>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\">\n\n\n\n<h2 class=\"wp-block-heading\">(iii) Find an expression that relates P and t, and explain why it represents linear growth.<\/h2>\n\n\n\n<figure class=\"wp-block-image size-large\"><img loading=\"lazy\" decoding=\"async\" width=\"1024\" height=\"683\" src=\"https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-785-1024x683.png\" alt=\"\" class=\"wp-image-5559\" srcset=\"https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-785-1024x683.png 1024w, https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-785-300x200.png 300w, https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-785-768x512.png 768w, https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-785-1200x800.png 1200w, https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-785.png 1536w\" sizes=\"(max-width: 1024px) 100vw, 1024px\"><\/figure>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\">\n\n\n\n<h1 class=\"wp-block-heading\">Question 4<\/h1>\n\n\n\n<p class=\"wp-block-paragraph\">A telecom company charges <code>600 for a certain recharge scheme. This prepaid balance is reduced by<\/code>15 each day after the recharge.<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\">\n\n\n\n<h2 class=\"wp-block-heading\">(i) Write an equation that models the remaining balance b(x) after using the scheme for x days. Explain why it represents linear decay.<\/h2>\n\n\n\n<h3 class=\"wp-block-heading\">Solution<\/h3>\n\n\n\n<figure class=\"wp-block-image size-large\"><img loading=\"lazy\" decoding=\"async\" width=\"1024\" height=\"683\" src=\"https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-786-1024x683.png\" alt=\"\" class=\"wp-image-5561\" srcset=\"https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-786-1024x683.png 1024w, https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-786-300x200.png 300w, https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-786-768x512.png 768w, https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-786-1200x800.png 1200w, https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-786.png 1536w\" sizes=\"(max-width: 1024px) 100vw, 1024px\"><\/figure>\n\n\n\n<p class=\"wp-block-paragraph\">Reduction every day = &#8377;15<math xmlns=\"http:\/\/www.w3.org\/1998\/Math\/MathML\" display=\"block\"><semantics><mrow><mi>b<\/mi><mo stretchy=\"false\">(<\/mo><mi>x<\/mi><mo stretchy=\"false\">)<\/mo><mo>=<\/mo><mn>600<\/mn><mo>&minus;<\/mo><mn>15<\/mn><mi>x<\/mi><\/mrow><annotation encoding=\"application\/x-tex\">b(x)=600-15x<\/annotation><\/semantics><\/math><\/p>\n\n\n\n<div class=\"internal-linking-related-contents\"><a href=\"https:\/\/mymockmate.com\/notes\/ncert-class-10-maths-real-number-exercise-1-2-solutions-mymockmate\/\" class=\"template-2\"><span class=\"cta\">Related Topic to Read more<\/span><span class=\"postTitle\">NCERT Class 10 Maths Real Number Exercise 1.2 Solutions |  MyMockMate<\/span><\/a><\/div><p class=\"wp-block-paragraph\">This represents <strong>linear decay<\/strong> because balance decreases by a fixed amount daily.<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\">\n\n\n\n<h2 class=\"wp-block-heading\">(ii) After how many days will the balance run out?<\/h2>\n\n\n\n<h3 class=\"wp-block-heading\">Solution<\/h3>\n\n\n\n<h3 class=\"wp-block-heading\"><\/h3>\n\n\n\n<figure class=\"wp-block-image size-large\"><img loading=\"lazy\" decoding=\"async\" width=\"1024\" height=\"683\" src=\"https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-787-1024x683.png\" alt=\"\" class=\"wp-image-5563\" srcset=\"https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-787-1024x683.png 1024w, https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-787-300x200.png 300w, https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-787-768x512.png 768w, https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-787-1200x800.png 1200w, https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-787.png 1536w\" sizes=\"(max-width: 1024px) 100vw, 1024px\"><\/figure>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\">\n\n\n\n<h2 class=\"wp-block-heading\">(iii) Make a table of values for x varying from 1 to 10 days and<br>show how the balance b(x), reduces with time.<\/h2>\n\n\n\n<figure class=\"wp-block-image size-large\"><img loading=\"lazy\" decoding=\"async\" width=\"1024\" height=\"683\" src=\"https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-788-1024x683.png\" alt=\"\" class=\"wp-image-5568\" srcset=\"https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-788-1024x683.png 1024w, https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-788-300x200.png 300w, https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-788-768x512.png 768w, https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-788-1200x800.png 1200w, https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-788.png 1536w\" sizes=\"(max-width: 1024px) 100vw, 1024px\"><\/figure>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\">\n\n\n\n<h1 class=\"wp-block-heading\">Common Mistakes<\/h1>\n\n\n\n<p class=\"wp-block-paragraph\">&#10060; Using wrong sign in growth and decay problems<br>&#10060; Forgetting initial value in expressions<br>&#10060; Calculation mistakes in tables<br>&#10060; Confusing increase with decrease<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\">\n\n\n\n<h1 class=\"wp-block-heading\">Exam Tips<\/h1>\n\n\n\n<p class=\"wp-block-paragraph\">&#10004; Growth means addition (+)<br>&#10004; Decay means subtraction (&minus;)<br>&#10004; Write formula before solving<br>&#10004; Make tables carefully and systematically<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\">\n\n\n\n<h1 class=\"wp-block-heading\">Practice MCQs<\/h1>\n\n\n\n<h2 class=\"wp-block-heading\">1. Which expression represents linear growth?<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">A) <math xmlns=\"http:\/\/www.w3.org\/1998\/Math\/MathML\"><semantics><mrow><mn>500<\/mn><mo>&minus;<\/mo><mn>20<\/mn><mi>x<\/mi><\/mrow><annotation encoding=\"application\/x-tex\">500-20x<\/annotation><\/semantics><\/math><br>B) <math xmlns=\"http:\/\/www.w3.org\/1998\/Math\/MathML\"><semantics><mrow><mn>1000<\/mn><mo>+<\/mo><mn>50<\/mn><mi>x<\/mi><\/mrow><annotation encoding=\"application\/x-tex\">1000+50x<\/annotation><\/semantics><\/math>1000+50x<br>C) <math xmlns=\"http:\/\/www.w3.org\/1998\/Math\/MathML\"><semantics><mrow><msup><mi>x<\/mi><mn>2<\/mn><\/msup><mo>+<\/mo><mn>5<\/mn><\/mrow><annotation encoding=\"application\/x-tex\">x^2+5<\/annotation><\/semantics><\/math><br>D) <math xmlns=\"http:\/\/www.w3.org\/1998\/Math\/MathML\"><semantics><mrow><msup><mn>2<\/mn><mi>x<\/mi><\/msup><\/mrow><annotation encoding=\"application\/x-tex\">2^x<\/annotation><\/semantics><\/math><\/p>\n\n\n\n<h3 class=\"wp-block-heading\">Answer<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">&#9989; B) <math xmlns=\"http:\/\/www.w3.org\/1998\/Math\/MathML\"><semantics><mrow><mn>1000<\/mn><mo>+<\/mo><mn>50<\/mn><mi>x<\/mi><\/mrow><annotation encoding=\"application\/x-tex\">1000+50x<\/annotation><\/semantics><\/math><\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\">\n\n\n\n<h2 class=\"wp-block-heading\">2. Which expression represents linear decay?<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">A) <math xmlns=\"http:\/\/www.w3.org\/1998\/Math\/MathML\"><semantics><mrow><mn>200<\/mn><mo>+<\/mo><mn>15<\/mn><mi>x<\/mi><\/mrow><annotation encoding=\"application\/x-tex\">200+15x<\/annotation><\/semantics><\/math><br>B) <math xmlns=\"http:\/\/www.w3.org\/1998\/Math\/MathML\"><semantics><mrow><mn>500<\/mn><mo>&minus;<\/mo><mn>10<\/mn><mi>x<\/mi><\/mrow><annotation encoding=\"application\/x-tex\">500-10x<\/annotation><\/semantics><\/math><br>C) <math xmlns=\"http:\/\/www.w3.org\/1998\/Math\/MathML\"><semantics><mrow><msup><mi>x<\/mi><mn>2<\/mn><\/msup><mo>&minus;<\/mo><mn>1<\/mn><\/mrow><annotation encoding=\"application\/x-tex\">x^2-1<\/annotation><\/semantics><\/math><br>D) <math xmlns=\"http:\/\/www.w3.org\/1998\/Math\/MathML\"><semantics><mrow><mn>3<\/mn><msup><mi>x<\/mi><mn>2<\/mn><\/msup><\/mrow><annotation encoding=\"application\/x-tex\">3x^2<\/annotation><\/semantics><\/math><\/p>\n\n\n\n<h3 class=\"wp-block-heading\">Answer<\/h3>\n\n\n\n<div class=\"internal-linking-related-contents\"><a href=\"https:\/\/mymockmate.com\/notes\/class-10-maths-exercise-2-1-solutions-polynomials-ncert-solutions\/\" class=\"template-2\"><span class=\"cta\">Related Topic to Read more<\/span><span class=\"postTitle\">NCERT Class 10 Maths Exercise 2.1 Solutions | Polynomials<\/span><\/a><\/div><p class=\"wp-block-paragraph\">&#9989; B) <math xmlns=\"http:\/\/www.w3.org\/1998\/Math\/MathML\"><semantics><mrow><mn>500<\/mn><mo>&minus;<\/mo><mn>10<\/mn><mi>x<\/mi><\/mrow><annotation encoding=\"application\/x-tex\">500-10x<\/annotation><\/semantics><\/math><\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\">\n\n\n\n<h2 class=\"wp-block-heading\">3. A value decreases by &#8377;100 every year. Which expression is correct?<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">A) <math xmlns=\"http:\/\/www.w3.org\/1998\/Math\/MathML\"><semantics><mrow><mn>500<\/mn><mo>+<\/mo><mn>100<\/mn><mi>x<\/mi><\/mrow><annotation encoding=\"application\/x-tex\">500+100x<\/annotation><\/semantics><\/math><br>B) <math xmlns=\"http:\/\/www.w3.org\/1998\/Math\/MathML\"><semantics><mrow><mn>500<\/mn><mo>&minus;<\/mo><mn>100<\/mn><mi>x<\/mi><\/mrow><annotation encoding=\"application\/x-tex\">500-100x<\/annotation><\/semantics><\/math><br>C) <math xmlns=\"http:\/\/www.w3.org\/1998\/Math\/MathML\"><semantics><mrow><mn>100<\/mn><mi>x<\/mi><mo>&minus;<\/mo><mn>500<\/mn><\/mrow><annotation encoding=\"application\/x-tex\">100x-500<\/annotation><\/semantics><\/math><br>D) <math xmlns=\"http:\/\/www.w3.org\/1998\/Math\/MathML\"><semantics><mrow><mn>500<\/mn><mi>x<\/mi><\/mrow><annotation encoding=\"application\/x-tex\">500x<\/annotation><\/semantics><\/math><\/p>\n\n\n\n<h3 class=\"wp-block-heading\">Answer<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">&#9989; B) <math xmlns=\"http:\/\/www.w3.org\/1998\/Math\/MathML\"><semantics><mrow><mn>500<\/mn><mo>&minus;<\/mo><mn>100<\/mn><mi>x<\/mi><\/mrow><annotation encoding=\"application\/x-tex\">500-100x<\/annotation><\/semantics><\/math><\/p><div class=\"mymoc-middle mymoc-entity-placement\" id=\"mymoc-3697564222\"><div id=\"mymoc-9907420\"><a href=\"https:\/\/amzn.to\/4ehJfM4\" aria-label=\"students acessories\"><img src=\"https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/06\/students-acessories.png\" alt=\"\" srcset=\"https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/06\/students-acessories.png 1301w, https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/06\/students-acessories-300x85.png 300w, https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/06\/students-acessories-1024x290.png 1024w, https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/06\/students-acessories-768x218.png 768w\" sizes=\"(max-width: 1301px) 100vw, 1301px\" width=\"1080\" height=\"100\"><\/a><\/div><\/div>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\">\n\n\n\n<h2 class=\"wp-block-heading\">4. Linear growth means:<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">A) Variable increase<br>B) Constant increase<br>C) Random increase<br>D) Quadratic increase<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">Answer<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">&#9989; B) Constant increase<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\">\n\n\n\n<h1 class=\"wp-block-heading\">FAQ Section<\/h1>\n\n\n\n<h2 class=\"wp-block-heading\">Q1. What is linear growth?<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">Linear growth means a quantity increases by a fixed amount over equal intervals.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\">Q2. What is linear decay?<\/h2>\n\n\n\n<div class=\"internal-linking-related-contents\"><a href=\"https:\/\/mymockmate.com\/notes\/class-10-maths-exercise-2-2-solutions-relationship-between-zeroes-and-coefficients\/\" class=\"template-2\"><span class=\"cta\">Related Topic to Read more<\/span><span class=\"postTitle\">Class 10 Maths Exercise 2.2 Solutions | Relationship Between Zeroes and Coefficients<\/span><\/a><\/div><p class=\"wp-block-paragraph\">Linear decay means a quantity decreases by a fixed amount over equal intervals.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\">Q3. What is a linear function?<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">A function represented by a straight-line equation is called a linear function.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\">Q4. Why are tables important in linear functions?<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">Tables help us understand patterns and relationships clearly.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\">Q5. Can real-life situations be represented using linear equations?<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">Yes, many daily-life situations can be represented using linear equations.<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\">\n\n\n\n<p class=\"wp-block-paragraph\">Practice more chapter-wise Maths solutions, MCQs, mock tests, and concept-based exercises on <strong><a target=\"_blank\" rel=\"noreferrer noopener\">MyMockMate<\/a><\/strong> and strengthen your Class 9 Mathematics preparation with smart learning resources!<\/p>\n<div class=\"pdfprnt-buttons pdfprnt-buttons-post pdfprnt-top-bottom-right\"><a href=\"https:\/\/mymockmate.com\/notes\/wp-json\/wp\/v2\/posts\/2134?print=print\" class=\"pdfprnt-button pdfprnt-button-print\" target=\"_blank\"><img decoding=\"async\" src=\"https:\/\/mymockmate.com\/notes\/wp-content\/plugins\/pdf-print\/images\/print.png\" alt=\"image_print\" title=\"Print Content\"><span class=\"pdfprnt-button-title pdfprnt-button-print-title\">Print<\/span><\/a> <span class=\"pdfprnt-count-generation\">24<\/span><\/div><div class=\"mymoc-bottom mymoc-entity-placement\" id=\"mymoc-762407308\"><div id=\"mymoc-2995665809\"><a href=\"https:\/\/amzn.to\/440rYSB\" aria-label=\"ssd\"><img src=\"https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/06\/ssd.png\" alt=\"\" srcset=\"https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/06\/ssd.png 1303w, https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/06\/ssd-300x50.png 300w, https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/06\/ssd-1024x171.png 1024w, https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/06\/ssd-768x128.png 768w\" sizes=\"(max-width: 1303px) 100vw, 1303px\" width=\"1303\" height=\"218\"><\/a><\/div><\/div>","protected":false},"excerpt":{"rendered":"<p> 24 Short Intro Exercise 2.4 explains the concepts of linear growth and linear decay using real-life situations like plant growth, mobile depreciation, population increase,&#8230;<\/p>\n","protected":false},"author":1,"featured_media":2137,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"postBodyCss":"","postBodyMargin":[],"postBodyPadding":[],"postBodyBackground":{"backgroundType":"classic","gradient":""},"footnotes":""},"categories":[22,4,11],"tags":[668,697,136,711,703,685,708,706,709,704,705,91,674,707,712,710,713],"class_list":["post-2134","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-cbse","category-class-9","category-maths-class-9","tag-algebraic-expressions","tag-class-9-algebra","tag-class-9-maths","tag-depreciation-problems","tag-exercise-2-4-solutions","tag-grade-9-mathematics","tag-growth-and-decay-maths","tag-linear-decay-questions","tag-linear-functions","tag-linear-growth-and-decay","tag-linear-growth-examples","tag-maths-chapter-2-solutions","tag-mymockmate-maths-solutions","tag-polynomial-chapter-solutions","tag-population-growth-questions","tag-table-of-values-maths","tag-telecom-recharge-balance-problems"],"featured_image_src":"https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/NCERT-Class-9-Maths-Exercise-2.4-Solutions-\u2013-Linear-Growth-and-Decay.png","author_info":{"display_name":"Team Mymockmate","author_link":"https:\/\/mymockmate.com\/notes\/author\/bsm_adm\/"},"_links":{"self":[{"href":"https:\/\/mymockmate.com\/notes\/wp-json\/wp\/v2\/posts\/2134","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/mymockmate.com\/notes\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/mymockmate.com\/notes\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/mymockmate.com\/notes\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/mymockmate.com\/notes\/wp-json\/wp\/v2\/comments?post=2134"}],"version-history":[{"count":20,"href":"https:\/\/mymockmate.com\/notes\/wp-json\/wp\/v2\/posts\/2134\/revisions"}],"predecessor-version":[{"id":5586,"href":"https:\/\/mymockmate.com\/notes\/wp-json\/wp\/v2\/posts\/2134\/revisions\/5586"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/mymockmate.com\/notes\/wp-json\/wp\/v2\/media\/2137"}],"wp:attachment":[{"href":"https:\/\/mymockmate.com\/notes\/wp-json\/wp\/v2\/media?parent=2134"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/mymockmate.com\/notes\/wp-json\/wp\/v2\/categories?post=2134"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/mymockmate.com\/notes\/wp-json\/wp\/v2\/tags?post=2134"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}