How many cubic metres of earth must be dug to construct a well 7m deep and diameter 2.8 m?

Solution:

The problem statement refers to the volume of the well which is 7m deep and diameter 2.8 metres.

The volume of cylinder is = πr²h

Where r = radius of the cylinder

h = height of the cylinder

In the problem statement r = 2.8/2 = 1.4m

The height or depth of the well = 7m

Therefore while digging a well with radius 1.4m and depth(height) = 7m the amount of earth that is dug out = πr²h = π × (1.4)² × (7) = (22/7) × (1.4)² × (7) = 43.12m³

✦ Try This: How many cubic metres of earth must be dug to construct a well 14m deep and diameter 3.5 m?

The problem statement refers to the volume of the well which is 14m deep and diameter 3.5 metres.

The volume of cylinder is = πr²h

Where r = radius of the cylinder

h = height of the cylinder

In the problem statement r = 3.5/2 = 1.75m

The height or depth of the well = 14m

Therefore while digging a well with radius 1.4m and depth(height) = 7m the amount of earth that is dug out = πr²h = π × (1.4)² × (7) = (22/7) × (1.75)² × (14) = 134.75m³

☛ Also Check: NCERT Solutions for Class 8 Maths Chapter 11

NCERT Exemplar Class 8 Maths Chapter 11 Problem 89

How many cubic metres of earth must be dug to construct a well 7m deep and diameter 2.8 m?

Summary:

43.12 cubic metres (m³ )of earth must be dug to construct a well 7m deep and diameter 2.8 m

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