{"id":449,"date":"2022-04-12T10:37:09","date_gmt":"2022-04-12T10:37:09","guid":{"rendered":"http:\/\/7thclass.deltapublications.in\/?page_id=449"},"modified":"2025-11-10T06:25:18","modified_gmt":"2025-11-10T06:25:18","slug":"w-5-circles-calculate-area-circumference-radius-and-diameter","status":"publish","type":"page","link":"https:\/\/7thclass.deltapublications.in\/index.php\/w-5-circles-calculate-area-circumference-radius-and-diameter\/","title":{"rendered":"W.5 Circles: calculate area, circumference, radius and diameter"},"content":{"rendered":"\n<h2 class=\"wp-block-heading has-text-align-center has-text-color\" style=\"color:#00056d;text-transform:uppercase\"><strong> Circles: calculate area, circumference, radius and diameter<\/strong><\/h2>\n\n\n\n<div class=\"wp-block-columns is-layout-flex wp-container-core-columns-is-layout-9d6595d7 wp-block-columns-is-layout-flex\">\n<div class=\"wp-block-column is-layout-flow wp-block-column-is-layout-flow\" style=\"flex-basis:100%\">\n<div style=\"position: relative; width: 100%; height: 0; padding-top: 56.2500%;\n padding-bottom: 0; box-shadow: 0 2px 8px 0 rgba(63,69,81,0.16); margin-top: 1.6em; margin-bottom: 0.9em; overflow: hidden;\n border-radius: 8px; will-change: transform;\">\n  <iframe loading=\"lazy\" style=\"position: absolute; width: 100%; height: 100%; top: 0; left: 0; border: none; padding: 0;margin: 0;\"\n    src=\"https:\/\/www.canva.com\/design\/DAG2-wg_vMk\/_jTeUToijo8pK3D3oXHGpQ\/watch?embed\" allowfullscreen=\"allowfullscreen\" allow=\"fullscreen\">\n  <\/iframe>\n<\/div>\n<a href=\"https:&#x2F;&#x2F;www.canva.com&#x2F;design&#x2F;DAG2-wg_vMk&#x2F;_jTeUToijo8pK3D3oXHGpQ&#x2F;watch?utm_content=DAG2-wg_vMk&amp;utm_campaign=designshare&amp;utm_medium=embeds&amp;utm_source=link\" target=\"_blank\" rel=\"noopener\">Design<\/a> by Delta publications\n<\/div>\n<\/div>\n\n\n\n<p class=\"has-text-color has-large-font-size\" style=\"color:#74008b\">key notes :<\/p>\n\n\n\n<figure class=\"wp-block-table\"><table class=\"has-text-color has-link-color has-fixed-layout\" style=\"color:#000060\"><tbody><tr><td><strong>Parts of a Circle<\/strong><\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n<p><strong>Center (O):<\/strong> The fixed point in the middle.<\/p>\n\n\n\n<p><strong>Radius (r):<\/strong> The distance from the center to any point on the circle.<\/p>\n\n\n\n<p><strong>Diameter (d):<\/strong> The longest chord, passing through the center. d=2rd = 2rd=2r<\/p>\n\n\n\n<p><strong>Circumference (C):<\/strong> The distance around the circle (its perimeter).<\/p>\n\n\n\n<figure class=\"wp-block-table\"><table class=\"has-text-color has-link-color has-fixed-layout\" style=\"color:#000060\"><tbody><tr><td><strong><strong>Formulas<\/strong><\/strong><\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n<p><strong>1. Radius and Diameter<\/strong><\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>d=2r<\/li>\n\n\n\n<li>r=d\/2<\/li>\n<\/ul>\n\n\n\n<p><strong>2. Circumference (Perimeter of Circle)<\/strong><\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>C=2\u03c0r or C=\u03c0d<\/li>\n<\/ul>\n\n\n\n<p><strong>3. Area of Circle<\/strong> A=\u03c0r<sup>2<\/sup><\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>\ud83d\udc49 Here, take <strong>\u03c0\u22483.14 or 22\/7\u200b<\/strong>.<\/li>\n<\/ul>\n\n\n\n<figure class=\"wp-block-table\"><table class=\"has-text-color has-link-color has-fixed-layout\" style=\"color:#000060\"><tbody><tr><td><strong><strong><strong>Examples<\/strong><\/strong><\/strong><\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n<h3 class=\"wp-block-heading has-normal-font-size\"><strong>Example 1: <\/strong>Find circumference<\/h3>\n\n\n\n<p>Radius = 7 cm <\/p>\n\n\n\n<p>C=2\u03c0r=2\u00d722\/7\u00d77=44\u2009cm<\/p>\n\n\n\n<h3 class=\"wp-block-heading has-normal-font-size\"><strong>Example 2:<\/strong> Find area<\/h3>\n\n\n\n<p>Radius = 10 cm<\/p>\n\n\n\n<p> A=\u03c0r<sup>2<\/sup>=3.14\u00d710<sup>2<\/sup>=314\u2009cm<sup>2<\/sup><\/p>\n\n\n\n<h3 class=\"wp-block-heading has-normal-font-size\"><strong>Example 3:<\/strong> Find radius when diameter is given<\/h3>\n\n\n\n<p>Diameter = 14 m <\/p>\n\n\n\n<p>r=d\/2=14\/2=7\u2009m<\/p>\n\n\n\n<h3 class=\"wp-block-heading has-normal-font-size\"><strong>Example 4: <\/strong>Find diameter from circumference<\/h3>\n\n\n\n<p>Circumference = 31.4 cm <\/p>\n\n\n\n<p>C=\u03c0d\u2005\u200a\u27f9\u2005\u200ad=C\/\u03c0=31.4\/3.14=10\u2009<\/p>\n\n\n\n<figure class=\"wp-block-table\"><table class=\"has-text-color has-link-color has-fixed-layout\" style=\"color:#000060\"><tbody><tr><td><strong><strong><strong><strong>Important Points<\/strong><\/strong><\/strong><\/strong><\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n<p>Always check whether <strong>radius or diameter<\/strong> is given.<\/p>\n\n\n\n<p>Use <strong>\u03c0=22\/7<\/strong> if radius\/diameter is a multiple of 7.<\/p>\n\n\n\n<p>Units:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>Circumference \u2192 cm, m, km (linear units)<\/li>\n\n\n\n<li>Area \u2192 cm\u00b2, m\u00b2, km\u00b2 (square units)<\/li>\n<\/ul>\n\n\n\n<figure class=\"wp-block-table\"><table class=\"has-text-color has-link-color has-fixed-layout\" style=\"color:#000060\"><tbody><tr><td><strong><strong><strong><strong><strong>Practice Questions<\/strong><\/strong><\/strong><\/strong><\/strong><\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n<ol class=\"wp-block-list\">\n<li>Find the circumference of a circle with radius 14 cm.<\/li>\n\n\n\n<li>A circle has diameter 20 cm. Find its radius and area.<\/li>\n\n\n\n<li>Find the area of a circle with radius 21 m (take \u03c0=22\/7\u200b).<\/li>\n\n\n\n<li>The circumference of a circle is 44 cm. Find its diameter and radius.<\/li>\n\n\n\n<li>A circular park has a radius of 35 m. Find its area and circumference.<\/li>\n<\/ol>\n\n\n\n<p class=\"has-text-align-center has-text-color has-huge-font-size\" style=\"color:#105000\"><strong>Learn with an example<\/strong><\/p>\n\n\n\n<div class=\"wp-block-group has-primary-color has-text-color has-background has-normal-font-size\" style=\"background-color:#b39ff4\"><div class=\"wp-block-group__inner-container is-layout-flow wp-block-group-is-layout-flow\">\n<div class=\"wp-block-group has-primary-color has-background-background-color has-text-color has-background\"><div class=\"wp-block-group__inner-container is-layout-flow wp-block-group-is-layout-flow\">\n<p class=\"has-text-color has-normal-font-size\" style=\"color:#b00012\">\u27a1\ufe0f <strong>The&nbsp;circumference of a circle is&nbsp;31.4&nbsp;metres. What is the circle&#8217;s&nbsp;diameter?<\/strong><\/p>\n\n\n<div class=\"wp-block-image\">\n<figure class=\"aligncenter size-full is-resized\"><img loading=\"lazy\" decoding=\"async\" width=\"500\" height=\"500\" src=\"https:\/\/7thclass.deltapublications.in\/wp-content\/uploads\/2023\/02\/Untitled-design-9-2.png\" alt=\"\" class=\"wp-image-5271\" style=\"aspect-ratio:1;width:328px;height:auto\" srcset=\"https:\/\/7thclass.deltapublications.in\/wp-content\/uploads\/2023\/02\/Untitled-design-9-2.png 500w, https:\/\/7thclass.deltapublications.in\/wp-content\/uploads\/2023\/02\/Untitled-design-9-2-300x300.png 300w, https:\/\/7thclass.deltapublications.in\/wp-content\/uploads\/2023\/02\/Untitled-design-9-2-150x150.png 150w, https:\/\/7thclass.deltapublications.in\/wp-content\/uploads\/2023\/02\/Untitled-design-9-2-400x400.png 400w\" sizes=\"auto, (max-width: 500px) 100vw, 500px\" \/><\/figure><\/div>\n\n\n<p>Use&nbsp;3.14 for&nbsp;\u200b\ud835\udf0b.&nbsp;<\/p>\n\n\n\n<p>______ metres<\/p>\n<\/div><\/div>\n\n\n\n<p>The&nbsp;circumference is&nbsp;31.4&nbsp;metres. Replace&nbsp;C&nbsp;by&nbsp;31.4&nbsp;in the&nbsp;formula.<\/p>\n\n\n\n<p>C=\u200b\ud835\udf0bd<\/p>\n\n\n\n<p>C\u22483.14d<\/p>\n\n\n\n<p>31.4\u00f73.14\u2248d<\/p>\n\n\n\n<p>10\u2248d<\/p>\n\n\n\n<p>The diameter is about 10 metres.<\/p>\n<\/div><\/div>\n\n\n\n<div class=\"wp-block-group has-primary-color has-text-color has-background has-normal-font-size\" style=\"background-color:#b6e69e\"><div class=\"wp-block-group__inner-container is-layout-flow wp-block-group-is-layout-flow\">\n<div class=\"wp-block-group has-primary-color has-background-background-color has-text-color has-background\"><div class=\"wp-block-group__inner-container is-layout-flow wp-block-group-is-layout-flow\">\n<p class=\"has-text-color\" style=\"color:#b00012\">\u27a1\ufe0f <strong>The&nbsp;circumference of a circle is&nbsp;25.12&nbsp;kilometres . What is the circle&#8217;s&nbsp;radius?<\/strong><\/p>\n\n\n<div class=\"wp-block-image\">\n<figure class=\"aligncenter size-full is-resized\"><img loading=\"lazy\" decoding=\"async\" width=\"500\" height=\"500\" src=\"https:\/\/7thclass.deltapublications.in\/wp-content\/uploads\/2023\/02\/Untitled-design-10-1.png\" alt=\"\" class=\"wp-image-5272\" style=\"aspect-ratio:1;width:397px;height:auto\" srcset=\"https:\/\/7thclass.deltapublications.in\/wp-content\/uploads\/2023\/02\/Untitled-design-10-1.png 500w, https:\/\/7thclass.deltapublications.in\/wp-content\/uploads\/2023\/02\/Untitled-design-10-1-300x300.png 300w, https:\/\/7thclass.deltapublications.in\/wp-content\/uploads\/2023\/02\/Untitled-design-10-1-150x150.png 150w, https:\/\/7thclass.deltapublications.in\/wp-content\/uploads\/2023\/02\/Untitled-design-10-1-400x400.png 400w\" sizes=\"auto, (max-width: 500px) 100vw, 500px\" \/><\/figure><\/div>\n\n\n<p>Use&nbsp;3.14 for&nbsp;\u200b\ud835\udf0b.&nbsp;<\/p>\n\n\n\n<p>______ kilometres<\/p>\n<\/div><\/div>\n\n\n\n<p>The&nbsp;circumference is&nbsp;25.12&nbsp;kilometres. Replace&nbsp;C&nbsp;by&nbsp;25.12&nbsp;in the&nbsp;formula.<\/p>\n\n\n\n<p>C=2\u200b\ud835\udf0br<\/p>\n\n\n\n<p>25.12\u224823.14r<\/p>\n\n\n\n<p>25.12\u22486.28r<\/p>\n\n\n\n<p>25.12\u00f76.28\u2248r<\/p>\n\n\n\n<p>4\u2248r<\/p>\n\n\n\n<p>The radius is about 4 kilometres.<\/p>\n<\/div><\/div>\n\n\n\n<div class=\"wp-block-group has-primary-color has-text-color has-background has-normal-font-size\" style=\"background-color:#e9e699\"><div class=\"wp-block-group__inner-container is-layout-flow wp-block-group-is-layout-flow\">\n<div class=\"wp-block-group has-primary-color has-background-background-color has-text-color has-background\"><div class=\"wp-block-group__inner-container is-layout-flow wp-block-group-is-layout-flow\">\n<p class=\"has-text-color\" style=\"color:#b00012\">\u27a1\ufe0f<strong> The&nbsp;diameter of a circle is&nbsp;8&nbsp;millimetres. What is the circle&#8217;s&nbsp;circumference?<\/strong><\/p>\n\n\n<div class=\"wp-block-image\">\n<figure class=\"aligncenter size-full is-resized\"><img loading=\"lazy\" decoding=\"async\" width=\"500\" height=\"500\" src=\"https:\/\/7thclass.deltapublications.in\/wp-content\/uploads\/2023\/02\/Untitled-design-11-2.png\" alt=\"\" class=\"wp-image-5273\" style=\"aspect-ratio:1;width:338px;height:auto\" srcset=\"https:\/\/7thclass.deltapublications.in\/wp-content\/uploads\/2023\/02\/Untitled-design-11-2.png 500w, https:\/\/7thclass.deltapublications.in\/wp-content\/uploads\/2023\/02\/Untitled-design-11-2-300x300.png 300w, https:\/\/7thclass.deltapublications.in\/wp-content\/uploads\/2023\/02\/Untitled-design-11-2-150x150.png 150w, https:\/\/7thclass.deltapublications.in\/wp-content\/uploads\/2023\/02\/Untitled-design-11-2-400x400.png 400w\" sizes=\"auto, (max-width: 500px) 100vw, 500px\" \/><\/figure><\/div>\n\n\n<p>Use&nbsp;3.14 for&nbsp;\u200b\ud835\udf0b.<\/p>\n\n\n\n<p>______ &nbsp;millimetres<\/p>\n<\/div><\/div>\n\n\n\n<p>The&nbsp;diameter is&nbsp;8&nbsp;millimetres. Replace&nbsp;d&nbsp;by&nbsp;8&nbsp;in the&nbsp;formula.<\/p>\n\n\n\n<p>C=\u200b\ud835\udf0bd<\/p>\n\n\n\n<p>\u22483.148<\/p>\n\n\n\n<p>\u224825.12<\/p>\n\n\n\n<p>The circumference is about 25.12 millimetres.<\/p>\n<\/div><\/div>\n\n\n\n<p class=\"has-text-color has-large-font-size\" style=\"color:#d90000\">Let&#8217;s practice!\ud83d\udd8a\ufe0f<\/p>\n\n\n\n<div class=\"wp-block-columns is-layout-flex wp-container-core-columns-is-layout-9d6595d7 wp-block-columns-is-layout-flex\">\n<div class=\"wp-block-column is-layout-flow wp-block-column-is-layout-flow\">\n<figure class=\"wp-block-image size-full\"><a href=\"https:\/\/wordwall.net\/play\/101654\/592\/921\"><img loading=\"lazy\" decoding=\"async\" width=\"500\" height=\"500\" src=\"https:\/\/7thclass.deltapublications.in\/wp-content\/uploads\/2023\/05\/Worksheet-1-2-129.png\" alt=\"\" class=\"wp-image-6884\" srcset=\"https:\/\/7thclass.deltapublications.in\/wp-content\/uploads\/2023\/05\/Worksheet-1-2-129.png 500w, https:\/\/7thclass.deltapublications.in\/wp-content\/uploads\/2023\/05\/Worksheet-1-2-129-300x300.png 300w, https:\/\/7thclass.deltapublications.in\/wp-content\/uploads\/2023\/05\/Worksheet-1-2-129-150x150.png 150w, https:\/\/7thclass.deltapublications.in\/wp-content\/uploads\/2023\/05\/Worksheet-1-2-129-400x400.png 400w\" sizes=\"auto, (max-width: 500px) 100vw, 500px\" \/><\/a><\/figure>\n<\/div>\n\n\n\n<div class=\"wp-block-column is-layout-flow wp-block-column-is-layout-flow\">\n<figure class=\"wp-block-image size-full\"><a href=\"https:\/\/wordwall.net\/play\/101654\/871\/930\"><img loading=\"lazy\" decoding=\"async\" width=\"500\" height=\"500\" src=\"https:\/\/7thclass.deltapublications.in\/wp-content\/uploads\/2023\/05\/Worksheet-1-1-1-131.png\" alt=\"\" class=\"wp-image-6885\" srcset=\"https:\/\/7thclass.deltapublications.in\/wp-content\/uploads\/2023\/05\/Worksheet-1-1-1-131.png 500w, https:\/\/7thclass.deltapublications.in\/wp-content\/uploads\/2023\/05\/Worksheet-1-1-1-131-300x300.png 300w, https:\/\/7thclass.deltapublications.in\/wp-content\/uploads\/2023\/05\/Worksheet-1-1-1-131-150x150.png 150w, https:\/\/7thclass.deltapublications.in\/wp-content\/uploads\/2023\/05\/Worksheet-1-1-1-131-400x400.png 400w\" sizes=\"auto, (max-width: 500px) 100vw, 500px\" \/><\/a><\/figure>\n<\/div>\n<\/div>\n\n\n\n<p><\/p>\n","protected":false},"excerpt":{"rendered":"<p>Circles: calculate area, circumference, radius and diameter Design by Delta publications key notes : Parts of a Circle Center (O): The fixed point in the middle. Radius (r): The distance from the center to any point on the circle. Diameter (d): The longest chord, passing through the center. d=2rd = 2rd=2r Circumference (C): The distance<a class=\"more-link\" href=\"https:\/\/7thclass.deltapublications.in\/index.php\/w-5-circles-calculate-area-circumference-radius-and-diameter\/\">Continue reading <span class=\"screen-reader-text\">&#8220;W.5 Circles: calculate area, circumference, radius and diameter&#8221;<\/span><\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"parent":0,"menu_order":0,"comment_status":"closed","ping_status":"closed","template":"","meta":{"om_disable_all_campaigns":false,"footnotes":""},"class_list":["post-449","page","type-page","status-publish","hentry","entry"],"aioseo_notices":[],"_links":{"self":[{"href":"https:\/\/7thclass.deltapublications.in\/index.php\/wp-json\/wp\/v2\/pages\/449","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/7thclass.deltapublications.in\/index.php\/wp-json\/wp\/v2\/pages"}],"about":[{"href":"https:\/\/7thclass.deltapublications.in\/index.php\/wp-json\/wp\/v2\/types\/page"}],"author":[{"embeddable":true,"href":"https:\/\/7thclass.deltapublications.in\/index.php\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/7thclass.deltapublications.in\/index.php\/wp-json\/wp\/v2\/comments?post=449"}],"version-history":[{"count":19,"href":"https:\/\/7thclass.deltapublications.in\/index.php\/wp-json\/wp\/v2\/pages\/449\/revisions"}],"predecessor-version":[{"id":17558,"href":"https:\/\/7thclass.deltapublications.in\/index.php\/wp-json\/wp\/v2\/pages\/449\/revisions\/17558"}],"wp:attachment":[{"href":"https:\/\/7thclass.deltapublications.in\/index.php\/wp-json\/wp\/v2\/media?parent=449"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}