The inner diameter of a circular well is 3.5 m. It is 10 m deep. Find

(i) Its inner curved surface area,

(ii) The cost of plastering this curved surface at the rate of Rs 40 per m²

Concept Used: The curved surface area of cylinder = 2πrh

Where, r = radius of the cylinder

H = height of the cylinder

Given:

Inner Diameter of well = 3.5 m

The depth of well = 10 m

Radius =

Assumption: Let r = radius of the base of the cylinder and h be the height of the cylinder.

Explanation:

Inner radius (r) of circular well = m

= 1.75 m

Depth (h) of circular well = 10 m

(i) Inner curved surface area = 2πrh

= 2 × × 1.75 × 10 m²

= (44 × 0.25 × 10) m²

= 110 m²

Therefore, the inner curved surface area of the circular well is 110 m².

(ii) Cost of plastering 1 m² area = Rs 40

Cost of plastering 100 m² area = Rs (110 × 40)

= Rs 4400

Therefore, the cost of plastering the CSA of this well is Rs. 4400.