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SSC CGL 2019 PYQ — Question 66

SSC CGL - 10th June 2019 - Shift 1 • Quantitative Aptitude • Q66

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What is the ratio of the mean proportional between 4.8 and 10.8 and the third proportional to 0.4 and 2.4?

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Correct answer: A

Explanation

Correct Answer is option 1 i.e. 1 : 2

Concept

Application

Mean proportional of x and y = √(x × y)

Third proportional of x and y = y2/x

Mean proportional of 4.8 and 10.8

= √(10.8 × 4.8) 

= √(9 × 1.2 × 1.2 × 4)

= √(1.2 × 1.2 × 36)

= √(1.2 × 6)2 = √(7.2)2 = 7.2

And

Third proportional of 0.4 and 2.4

= 2.42/0.4 = 14.4

Hence, ratio = 7.2 : 14.4 = 1 : 2