Question

a well of diameter 7 m and height 20 m is dug out. find the cost of plastering the curved surface of the well at the rate of 20 per m²​

Answer 1

Answer:

The shape of the well is considered to be cylindrical as shown in the figure.

Given:

Depth (h) of well =20 m

Radius (r) of circular end of well =

2

7

m

Area of platform = Length x Breadth =22×14m

2

Assume height of the platform =H m

The volume of soil dug from the well will be equal to the volume of soil in platform.

Volume of soil from well = Volume of platform

⟹πr

2

h = Area of platform x Height of platform

π×(

2

7

)

2

×20=22×14×H

H=

7

22

×

4

49

×

22×14

20

H=

2

5

=2.5 m

Hence, the height of such a platform will be 2.5 m .