Question

a well of inner diameter 14 m is dug to a depth of 15 m. Earth taken
ut of it has been evenly spread all around it to a width of 7 m to
an embankment. Find the height of the embankment so formed.
​

Answer 1

Let the height of embankment be h.

Volume of earth taken out = πr2hπr2h

= 227×(7)2×15227×(7)2×15

Embankment >>!IMAGE!<<

Volume of earth taken out = Volume of embankment

[an embankment is a heap of stone or mud or earth to stop water]

πr2h=π(r1+r2)2h−πr21hπr2h=π(r1+r2)2h−πr12h

[Because r1=7,r2=7r1=7,r2=7]

=> 227×72×15=227(142−72)h227×72×15=227(142−72)h

Therefore, h=72×15196−49=5mh=72×15196−49=5m