Question

A well with 14m diameter of is dug 8m deep. The earth taken out of it has been evenly spread all around it in the shape of a circular ring of width 21m to form an embankment. Find the height of the embankment.

Answer 1

Radius of the well (r) = 3/2 m = 1.5 m

Height of the well(h) = 14 m

Volume of the earth taken out of the well = πr2h = 22 7 ×(1.5)2×14 = 99 m3 .

Outer radius of the embankment R = 3/2 + 7 = 17 / 2 m

Area of embankment = outer area - inner area

⇒ πR2 - πr2 = (22/7)(17/2)2 - (22/7)(3/2)2

⇒ 22x17x17/28 - 22x9x9 / 28= 6358 / 28 - 198 / 28

= 6160 / 28 = 220 m2

∴ Height of the embankment = Volume / area = 99 / 220 = 9/20 = 0.45 m.


Hope dis helps u

Answer 2

Radius of the well (r) = 3/2 m = 1.5 m

Height of the well(h) = 14 m

Volume of the earth taken out of the well = πr2h = 22 7 ×(1.5)2×14 = 99 m3 .

Outer radius of the embankment R = 3/2 + 7 = 17 / 2 m

Area of embankment = outer area - inner area

⇒ πR2 - πr2 = (22/7)(17/2)2 - (22/7)(3/2)2

⇒ 22x17x17/28 - 22x9x9 / 28= 6358 / 28 - 198 / 28

= 6160 / 28 = 220 m2

∴ Height of the embankment = Volume / area = 99 / 220 = 9/20 = 0.45 m.

Hope dis helps u