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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 :
Answer & Solution
Correct Answer:
Option
A
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
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
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