Question
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:
Answer: Option A
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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) = √400 = 20
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