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Target question: What is the value of K ?ardz24 wrote:If mn = K, what is the value of K ?
(1) m + n = 2mn
(2) (m + n)² = m²+ n²
Given: mn = K
Statement 1: m + n = 2mn
Since mn = K, we can rewrite statement 1 as: m + n = 2K
There are several values of m, n and K that satisfy statement 1. Here are two:
Case a: m = 1, n = 1 and K = 1. In this case, K = 1
Case b: m = 0, n = 0 and K = 0. In this case, K = 0
Since we cannot answer the target question with certainty, statement 1 is NOT SUFFICIENT
Statement 2: (m + n)² = m² + n²
Expand left side to get: m² + 2mn + n² = m²+ n²
Subtract m² from both sides to get: 2mn + n² = n²
Subtract n² from both sides to get: 2mn = 0
Divide from both sides by 2 to get: mn = 0
Since mn = K, we can be certain that K = 0
Since we can answer the target question with certainty, statement 2 is SUFFICIENT
Answer: B
Cheers,
Brent
