jamifahad wrote:

The positive integers r, s, and t are such that r is divisible by s and s is divisible by t. Is r even?

(1) st is odd.

(2) rt is even.

r/s->Integer

s/t->Integer

(1) st is odd.

Both s and t are odd.

r=9; s=3; t=1

r=6; s=3; t=1

Not Sufficient.

(2) rt is even.

Either r or t or both are even.

r=even. Fantastic.

t=Even; s becomes even; t has to be even.

See this:

s/t=Integer; t=Even; s=Even*Integer=Even;

r/s=Integer; s=Even; r=Even*Integer=Even;

So, r is definitely even.

Sufficient.

Ans: "B"

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~fluke