SSC CGL 2020 PYQ — Question 68

SSC CGL - 3rd March 2020 Shift 1 • Quantitative Aptitude • Q68

If the base radius of 2 cylinders are in the ratio 3 : 4 and their heights are in the ratio 4 : 9, then the ratio of their volumes is:

Show answer & explanation

Correct answer: C

Explanation

The correct answer is Option 3 i.e. 1 : 4

Given :

Base radius ratio = r1 : r2 = 3 : 4

Height ratio = h1 : h2 = 4 : 9

Formula used :

Volume of cylinder = πr2h\pi r^2h           ------ (1)

Calculations :

Using equation (1), we get

Let the radius of the cylinders be r1 and r2 and height be h1 and h2

According to the question, we have

⇒ Volume(V1) of first cylinder : Volume(V2) of second cylinder

⇒ V1 : V2 =  πr12h1\pi r_1^2h_1 : πr22h2\pi r_2^2h_2

⇒ V1 : V2 = (3)2 × 4 : (4)2 × 9

⇒ V1 : V2 = 9 × 4 : 16 × 9

⇒ V1 : V2 = 36 : 144

⇒ V1 : V2 = 1 : 4

 

Short trick :

Understanding Application
Tricks The volume of the 1st cylinder/Volume of the 2nd cylinder = 

πr12h1/πr22h2

= [3 × 3 × 4]/[4 × 4 × 9]

= 1/4

Hence 1 : 4