Question

How many cubic metres of earth must be dug
out to make a well 28 m deep and 2.8 m in
diameter ? Also, find the cost of plastering its
inner surface at rupees4.50 per sq. metre.​

Answer 1

Step-by-step explanation:

You have limited access to toppr answr. Sign to unlock 35 lakh questions

What's your doubt?

Biology

Bookmark

How many cubic metres of earth must be dug out to make a well 28 m deep and 2.8 m in diameter? Also, find the cost of plastering its inner surface at Rs.4.50 per sq.m.

share

Share

Answer

Correct option is

C

172.48 m

3

; Rs. 1108.80

Given, Earth has to dug out to make well 2.8 m in diameter and 28 m in height.

Also cost of plastering the inner wall is 4.50 per sq. m

Radius =

2

Diameter

=1.4 m

Well is cylindrical in shape.

So,

Volume of well to be dug out =πr

2

h

⇒V=

7

22

×1.4

2

×28

⇒V=172.48 m

3

To find cost of plastering of we have to first find curved surface area of inner wall.

Curved surface area =2πrh

⇒CSA=2×

7

22

×1.4×28

⇒CSA=246.4 m

2

Cost of plastering = Curved Surface Area× Rate per sq. meter

Cost =246.4×Rs. 4.50

⇒ Cost =Rs.1108.8