CAT 2018 Question Paper | CAT Verbal Ability Slot 1
Question :
While multiplying three real numbers, Ashok took one of the numbers as 73 instead of 37. As a result, the product went up by 720. Then the minimum possible value of the sum of squares of the other two numbers is:
Started 1 month ago by Shashank in
Answer : The answer is '40'
Explanatory Answer
Let the three real numbers be a, b, c. c is taken as 73 instead of 37
So, 73ab = 37ab + 720
36 ab = 720
ab = 720/36 = 20
We know, AM ≥ GM
(a²+b²) / 2 ≥ ab
(a 2 + b 2 ) ≥ 2ab
(a 2 + b 2 ) ≥ 40
(Or)
ab = 20
(a,b) = (√20, √20)
(a 2 + b 2 ) = 20 + 20 = 40
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