Question
A borewell of 28m base radius is digged upto a depth of
21m and 14m wide platform was made around the well. Find the height of platform?Solution
Volume of cylinder = 22/7 × (28)² × 21 = 51,744 Area of the platform to be filled = π (42)² - π (28)² = π × 70 × 14 [since volume will be the same] ⇒ 22/7 × 70 × 14 × h = 51,744  ⇒ h = 16.8m
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