Find the cost of plastering the inner surface of a well at Rs. `9. 50\ p e r\ m^2,` if it is 21m deep and diameter of its top is 6m.

Explanation

Height of cylinder =` 21m`
Diameter of cylinder = `6m`
Radius of cylinder = `6/2 = 3m`
Curved surface area of cylinder =` 2pirh`
` 2 xx22/7 xx 3 xx21`
`396 m^2 `
Cost of plastering the inner surface at the rate of `Rs 9.50 per m^2`
`396 xx 9.50 = Rs 3762`