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A 5-m-deep cylindrical pit having a radius of 1.4 m is dug in a field. The earth so dug out is used to raise a platform of 10 m × 8 m. What is the height of the platform (in cm)?

\(\left( {\text{Use}\,\pi = \frac{{22}}{7}} \right)\)


1. 38.5
2. 7.7
3. 137.5
4. 30

1 Answer

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Best answer
Correct Answer - Option 1 : 38.5

Given:

Radius of a cylinder = 1.4 m 

Height of a cylinder = 5m

The earth raise platform  = 10 × 8 × h

Concept Used:

Volume of cylinder = πr2h where r is the radius of the base and h is the height of the cylinder

Volume of cuboid = Length × Breadth × Height

Calculations:

Volume of a cylinder = volume of cuboid 

⇒ (22/7) × 1.4 × 1.4 × 5 = 10 × 8 × h

⇒ (22/7) × 1.4× 0.7 = 8 × h

⇒ h = (22/7) × 1.4 × 0.7/8

⇒ h = 0.385 m

⇒ h = 38.5 cm

∴ The height of the platform is 38.5 cm

1m = 100 cm

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