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SSC CGL 2017 PYQ — Question 1

SSC CGL Tier II Quant - 12/01/2017 • Quantitative Aptitude • Q1

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Twenty one times of a positive number is less than its square by 100. The value of the positive number is

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Correct answer: A

Explanation

The correct answer is Option 1 i.e. 25

Understanding

Application

Suppose the given number is ‘A’

So we have:

A2 – 21A = 100

A2 – 21A – 100 = 0

A2 – 25A + 4A – 100 = 0

A(A – 25) + 4(A – 25) = 0

(A – 25) (A + 4) = 0

A = 25

A = -4 (Not Possible as the number is positive)

Hence,

Number = 25