A dinner plate is in the form of circle. A circular region encloses a beautiful design as shown in the given figure. The inner circumference is 352 mm and outer is 396 mm. - Mathematics

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Sum

A dinner plate is in the form of circle. A circular region encloses a beautiful design as shown in the given figure. The inner circumference is 352 mm and outer is 396 mm. Find the width of circular design.

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Solution

Let the radius of inner and outer circle be rand R, respectively.

Given, inner circumference = 352 mm

⇒ 2πr = 352  ......[∵ Circumference = 2πr]

⇒ `2 xx 22/7 xx r` = 352

⇒ r = `(352 xx 7)/(2 xx 22) = 2464/44` = 56 mm

and outer circumference = 396 mm  .....[Given]

⇒ 2πr = 396

⇒ `2 xx 22/7 xx R` = 396

⇒ R = `(396 xx 7)/(2 xx 22)` = 63 mm

∴ Width of circular design = R – r = 63 – 56 = 7 mm

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Chapter 9: Perimeter and Area - Exercise [Page 298]

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NCERT Exemplar Mathematics Class 7
Chapter 9 Perimeter and Area
Exercise | Q 129. | Page 298

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