Aptitude - Problems on Numbers - Discussion

Discussion :: Problems on Numbers - General Questions (Q.No.7)

7.

The sum of the squares of three numbers is 138, while the sum of their products taken two at a time is 131. Their sum is:

 [A]. 20 [B]. 30 [C]. 40 [D]. None of these

Explanation:

Let the numbers be a, b and c.

Then, a2 + b2 + c2 = 138 and (ab + bc + ca) = 131.

(a + b + c)2 = a2 + b2 + c2 + 2(ab + bc + ca) = 138 + 2 x 131 = 400.

(a + b + c) = 400 = 20.

 Kailash said: (Nov 9, 2011) Why not it is (a + b + c)^2??

 Sai Kumar said: (Oct 7, 2014) How to find a, b, c values? If asked in the question?

 Yashable said: (Apr 23, 2015) And the following three numbers are 8, 7, 5 which is 64+49+25 = 138. And also 8+7+5 = 20.

 Bhupathi said: (Jul 30, 2015) Any more easiest method?

 Geetha said: (Sep 26, 2015) They ask just sum why you take (a+b+c)^2?

 Najar said: (Jan 10, 2017) Please tell me the answer for this qestion in detail.

 Johrge Kutty said: (Jan 28, 2017) @KAILASH. (A+B+C)^2 400 And they asked only sum. ie (A + B + C) = sqrt(400) = 20.