SarkariPYQ

SSC CGL 2019 PYQ — Question 70

SSC CGL - 12th June 2019 - Shift 3 • Quantitative Aptitude • Q70

Back to paper

If a – b = 5 and ab = 2, then a3– b3 is equal to:

Show answer & explanation

Correct answer: B

Explanation

Correct Answer is option 2 i.e.155

Concept

Understanding

Application

(a – b)3 = a3 – b3 – 3ab (a – b)

Given

a – b = 5

and

ab = 2

Applying the formula:

53 = a3 – b3 – 3 × 2 × 5

⇒a3 – b3 = 125 + 30

⇒a3 – b3 = 155