Question

A well with 10 m inside diameter is dug 8.4 m deep. Earth taken out of it is spread all around it to a width of 7.5 m to form an embankment. Find the height of the embankment.

Answer 1

We have,

Diameter of well = 10 m

Radius of well = d/2 = 10/2 = 5m

Depth of well = 8.4 m

Volume of earth dug out from well = πr²h

= 22/7 × 5 × 5 × 8.4

= 660 m³

This earth is spread out on width of 7.5 m.

inner radii, r = 5m and outer radii, R = (5+7.5) = 12.5cm

Area × h = 660

π(R² – r²) h = 660

π(12.5² – 5²) h = 660

22/7 (131.25) h = 660

h = 660×7 / 22×131.25

= 4620/2887.5

= 1.6 m

∴ Height of embankment is 1.6m.