QA – Placement Quizzes | Numbers, LCM and HCF | Question 14

Two numbers are in the ratio of 5:7. If their LCM is 105, what is the difference between their squares ?
(A) 216
(B) 210
(C) 72
(D) 840


Answer: (A)

Explanation: Let ‘h’ be the HCF of the two numbers.
=> The numbers are 5h and 7h.
We know that Product of Numbers = LCM x HCF
=> 5h x 7h = 105 x h
=> h = 3
So, the numbers are 15 and 21.
Therefore, difference of their squares = 21² – 15² = 441 – 225 = 216

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