Question

The outer circumference of a circular track is 528 m.The track is 14 m wide everywhere.calculate the cost of levelling the track at the rate of .50 per sq m

Answer 1

$Circumference = 2 \pi *radius$
528 = 2 * 22/7 * Radius
Radius = 528 * 7 / 22 * 2
= 528 * 7 / 44
= 12 * 7
= 84 m.

Now, 
Area of track = Area of outer circle - Area of inner circle

Radius of the inner circle = Radius of outer circle - Width of the track.
= 84 - 14
= 70 m.

Area of the track  :---
$Area = \pi R^{2} - \pi r^{2}$

where R = radius of the outer circle
& r = radius of the inner circle

Now,

Area of the track = 22/7 * 84*84 - 22/7*70*70
= 22/7 * ( 64*84 - 70*70)
= 22/7 * [ 7056 - 4900 ]
= 22/7 * 2156
= 6776 sq.metres.

Area of the track = 6776 sq.m

Rate of paving = Rs. 0.5 / sq .m 

So.,
The cost of paving = Area * Rate
= 6776 * 0.5
= Rs. 3388

Cost of paving the track = Rs. 3388

Answer 2

above picture will help you

be carefull because it is a long sum

and Happy study