Question

A well 20 m deep and of diameter 7 m is constructed. Find the volume of the earth taken out to construct the well. Also, find the cost of plastering the inner surface of the well at * 5 per square metre.​

Answer 1

Answer :

770 cubic metres.

Step-by-step explanation:

We have the diameter of the well = 7m.

And the radius of the well = 3.5m.

so, Depth of the well = h = 20m.

Hence the volume of the earth removed by digging =πr2h=227×(3.5)2×20=770 cubic metres.

idk if it's the answer u r looking for. :|

Answer 2

Answer:

hence, Earth to be dug out is 770m² .

and

cost of plastering the inner surface is Rs.2200

Step-by-step explanation:

we have,

volume of earth to be dug out = volume of well

$\frac{22}{7} \times \frac{7}{2} \times \frac{7}{2} \times 20 \\ = > 11 \times 7 \times 10 \\ = > 770 \: {m}^{2}$

Area of inner curved surface = 2πrh

$2 \times \frac{22}{7} \times \frac{7}{2} \times 20 \\ = > 44 \times 10 = 440 \: {m}^{2}$

Cost of plastering the inner surface = ( 440 × 5 )

= Rs.2200

hope this answer helps you dear...take care!