A well with an internal diameter 10 m is dug to a depth of 10 m. Earth taken out of it is spread all around the well to a width of 12 m to form an embankment. What is the height (in m, rounded off to 2 decimal places) of the embankment?
Show answer & explanation
Correct answer: C
Explanation
The correct answer is option 3 i.e. 0.95.
Volume of earth dug (well is a cylinder):
= π × (radius)² × height
= 3.1416 × (5)² × 10 = 3.1416 × 25 × 10 = 785.4 m³
Volume of embankment (a ring-shaped area):
Outer radius = 5 + 12 = 17 m, inner radius = 5 m
Area = π × (17² - 5²) = 3.1416 × (289 - 25) = 3.1416 × 264 = 829.38 m²
Let height of embankment = h
So, volume = 829.38 × h = 785.4
=> h = 785.4 ÷ 829.38 ≈ 0.95 m