Question

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The inner diameter of a circular well is 3.5 m. It is 10 m deep. Find
(1) its inner curved surface area,
(2) the cost of plastering this curved surface at the rate of 40 per m2.​

Answer 1

(1 ) Inner curved surface area of the well is 109.9 sq. meters.

(2) The cost of plastering the total curved surface area is 4396.

Explanation:

The inner diameter = 3.5 m

Depth of the well = 10 m

Now, Diameter = 2 x Radius

⇒R = D/ 2 = 3.5/2 = 1.75

or, the inner radius of the well = 1.75 m

CURVED SURFACE AREA of cylinder = 2πr h

⇒The inner curved surface area = 2πr h = 2 ( 3.14) (1.75)(10)

= 109 sq. meters

Hence, the inner curved surface area of the well is 109.9 sq. meters.

Now, the cost of plastering the curved area is 40 per sq meters

So, the cost of total plastering total area = 109.9 x(Cost per meter sq.)

= 109.9 x (40)

= 4396

Hence, the cost of plastering the total curved surface area is 4396.