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The Radii of the Inner and Outer Circumferences of a Circular Running Track Are 63 M and 70 M Respectively. Find : (I) the Area of the Track ; (Ii) the Difference Between the Lengths of the Two. - Mathematics

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Sum

The radii of the inner and outer circumferences of a circular running track are 63 m and 70 m respectively. Find :
(i) the area of the track ;
(ii) the difference between the lengths of the two circumferences of the track.

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Solution

Outer radius, r= 70 m

Inner radius, r= 63 m

∴ Area of track = `pir_1^2 - pir_2^2`

= `22/7[(70)^2 - (63)^2]`

= `22/7(70 + 63)(70 - 63)`

= `22/7 xx 133 xx 7`

= 2926 m2

Length of outer edge i.e. circumference

= `2pir_1`

= `2 xx 22/7 xx 70 = 440`m

Length of inner edge = `2pir_2`

= `2 xx 22/7 xx 63 = 396` m

Difference between lengths of two circumferences = 440 – 396 = 44 m
Hence (i) 2926 m2 (ii) 44 m

Concept: Area of Circle
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APPEARS IN

Selina Concise Mathematics Class 8 ICSE
Chapter 20 Area of a Trapezium and a Polygon
Exercise 20 (D) | Q 7 | Page 234
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