Question

Diameter of circular path is 140m around it on the outside a path in having width of 7 m is constructing if the path has to be fenced from inside and outside at the rate of rupees 7 per metre find its total cost

Answer 1

First of all find area of inner circle with diameter 140 m

then radius be = 140/2 = 70m

Area of inner circle = πr^2 = 22/7 × (70)^2

Area of inner circle = 22 × 10 × 70 = 15400 m^2

Now, find the area of inner circle with outer circular region which is 7m wide

Diameter of big circle = 140 + 7 + 7 = 154m

(since the outer circular region is 7m wider than inner, we have to add 7 from both sides of the inner circle to make the diameter of big circle)

radius of big circle = 154/2 = 77m

area of big circle = π(R)^2 = 22/7 × (77)^2

area of big circle = 22 × 11 × 77 = 18634 m^2

Now, to find the area of outer path

Area of outer circular path = Area of big circle - Area of inner circle

Area of outer circular path = 18634 - 15400

Area of outer circular path = 3234 m^2

cost is rs 7 per metre

Total cost = 3234 × 7

Total cost of fencing = rs 22638