The sum of the squares of three numbers is 138, while the sum of their product taken two at a time is 131. Their sum is :
A. 20
B. 30
C. 40
D. None of these
Answer: Option A
Solution(By Examveda Team)
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 × 131
= 400
⇒ (a + b + c) = $$\sqrt {400} $$ = 20
Related Questions on Problems on Numbers
If one-third of one-fourth of a number is 15, then three-tenth of that number is:
A. 35
B. 36
C. 45
D. 54
E. None of these
A. 9
B. 11
C. 13
D. 15
E. None of these
A. 3
B. 4
C. 9
D. Cannot be determined
E. None of these
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