Target Exam

CUET

Subject

General Test

Chapter

Quantitative Reasoning

Topic

Mensuration: 3D

Question:

A cylindrical rod of iron, whose height is equal to the radius of its base, is melted and cast into spherical balls, each of whose radius is half the radius of the base of the rod. Find the number of spherical balls thus made.

Options:

4

6

5

3

Correct Answer:

6

Explanation:

We know that,

Volume of a sphere = \(\frac{4}{3}\)πR3 

Volume of a cylinder = πR2H

Let the radius of the rod = 2x

and the height of the rod = 2x

So, the radius of each spherical ball = \(\frac{2x}{2}\) = x

let the number of the balls = a

According to the concept,

π × (2R)2 × 2R = \(\frac{4}{3}\) × π × R3 × a

= 8πR= \(\frac{4π }{3}\) × R3 × a 

= a = 6