GMAT Quantitative Reasoning Practice Test 7

There is a trick to this question, the time until both swimmers finish swimming 1500 meters is the time it takes the slower swimmer among the two to finish swimming.
Statement (1) tells us the rate of Andy, we can calculate the time it would take him to finish 1500 meters. This statement is insufficient by itself since we don’t know that Andy is slower than Tim.
Statement (2) completes statement (1) by telling us that Tim is faster and so the time is determined by Andy’s time. Both statements, taken together, are sufficient.