Question

A road 3.5 M wide surrounds a circular plot whose circumference is 44 M find the cost of paving the road at rupees 20 per metre square

Answer 1

Let the 'r' and 'R' be the radii of the inner and outer circle respectively.
Circumference of the circle = 44 m
2πr = 44
2*22/7*r = 44
r = (44*7)/44
r = 7 m
So, the radius of the inner circle is 7 m
Width of the road = 3.5 m
So, radius of the outer circle = 7 + 3.5 = 10.5 m
Area of the road = πR² - πr²
= 22/7*10.5*10.5 - 22/7*7*7
= 346.5 - 154
Area of the road = 192.5 sq m
Cost of paving the road = Rs. 50 per sq m
Total cost of paving the road = 192.5 × 50
Total cost = Rs. 9625