Question

The inner diameter of a circular well is 2.8 m.it is 8 m deep.Find the cost of plastering the inner curved sirface at the rate of rs.60 per m square


step by step explanations

right answer according to the answer sheet is rs.5913.60​

Answer 1

We know that the curved surface area of a right circular cylinder with radius r and height h is CSA=2πrh.

It is given that the height of the circular well is h=10 m and the diameter of the circular well is 2.8 m, and therefore the radius of the well is

2.8/2

=1.4 m, therefore,

CSA=2πrh=2×22/7 ×1.4×8=70.4 msquare

Therefore, the inner curved surface area is 70.4 m square

.

Also, the cost of plastering curved surface per m square

is Rs.60

Therefore, the cost of plastering 70.4 m square

is:

Rs.60×70.4m

= Rs.4224

Hence, the inner curved surface area is 70.4 m square

and the cost of plastering curved surface per m square

is Rs.60 is Rs.4224