rxs0005 wrote:
If j and k are integers and j^2/k is odd, which of the following must be true ?
(A) j and k are both even
(B) j = k
(C) If j is even, k is even
(D) j is divisible by k
(E) j^2 > k
Let’s check each answer choice using numbers.
(A) j and k are both even
Let’s say j = 3 and k = 1: we have 3^2/1 = 9, but neither j nor k is even. So, A is not the answer.
(B) j = k
Let’s say j = 3 and k = 1: we have 3^2/1 = 9, but j is not equal to k. So, B is not the answer.
(C) If j is even, k is even
This is an “if-then” statement. The only way this is false is if we can find an even number j and an odd number k and still have j^2/k = odd. However, if j is even, then j^2 is even. If j^2 is even and k is odd, and if j^2 is divisible by k, then j^2/k must be even since even/odd can’t ever be odd. So, we can’t find any even number j and odd number k such that j^2/k = odd, and thus C must be the correct answer. However, let’s also check why the last two answer choices can’t be correct.
(D) j is divisible by k
Let’s say j = 2 and k = 4: we have 2^2/4 = 1, but j is not divisible by k. So, D is not the answer.
(E) j^2 > k
Let’s say j = 1 and k = 1: we have 1^2/1 = 1, but j^2 is not greater than k. So, E is not the answer.
Answer: C
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