Question

The inner radius of a circular well is 1.75 m and it is 10 m deep. Find the cost of plastering its curved surface area at the rate of ₹ 20 per m².

Answer 1

Given:

Inner radius r = 1.75 m

depth (height) h = 10 m

rate = ₹20 per m².

Curved surface area (CSA) of the well

= 2πrh

= 2 × `22/7` × 1.75 × 10

1.75 × 10 = 17.5

2 × 22 = 44

CSA = `(44 × 17.5)/7​`

= `770/7 = 110 m^2`

= 110 m²

Cost of plastering = CSA × rate

= 110 × 20

= ₹2,200.