Book: RS Aggarwal - Mathematics
Chapter: 18. Area of Circle, Sector and Segment
Subject: Maths - Class 10th
Q. No. 17 of Formative Assessment (Unit Test)
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17
A racetrack is in the form of a ring whose inner circumference is 352 m and outer circumference is 396 m. Find the width and the area of the track.
Let the inner radius be R1 and outer radius be R2
Inner circumference = 2πR1 = 352 m
⇒ 2 × 22/7 × R1 = 352 m
⇒ R1 = 352 × 1/2 × 7/22
⇒ R1 = 56 m
Outer Circumference = 2πR2 = 396 m
⇒ 2 × 22/7 × R2 = 396 m
⇒ R2 = 396 × 1/2 × 7/22 m
⇒ R2 = 63 m
Width of the track = R2 – R1 = 63 m – 56 m = 7 m
Area of track = 
= 22/7 × (632 -562)
= 22/7 × (3969 – 3136) m2
= 22/7 × 833 m2 = 2618 m2
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