Question

223
into a cylinder along its length. Find the surface area of this cylinder.
A cylindrical well is 21 m deep. Its outer and inner diameters are 21 cm
14 m respectively. Find the cost of renovating the inner curved surface and
curved surface at the rate of 25 per m2. ​

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

2.8

=1.4 m, therefore,

CSA=2πrh=2×

7

22

×1.4×10=

7

616

=88 m

2

Therefore, the inner curved surface area is 88 m

2

.

Also, the cost of plastering curved surface per m

2

is Rs.42,

Therefore, the cost of plastering 88 m

2

is:

Rs.42×88 m

2

= Rs.3696.

Hence, the inner curved surface area is 88 m

2

and the cost of plastering curved surface per m

2

is Rs.42 is Rs.3696.