Explanation

Three robots!? Ejecting water!? What madness is this?! It's just a rate question. The common and careful phrases here are "independently and simultaneously" and "at a characteristic, constant rate." They mean that each robot works at a rate defined by a fraction, and that the combined rate is nothing other than the sum of the individual rates. So the information in the question means we can write:



Each of the T's represents a time, and each fraction is a rate with the units, . For example, the right-most fraction says that the robots together fill 1 pool (the top of the fraction) in 10 minutes. The left-most fraction indicates that Robot Q, if working alone, would fill 1 pool (the top of the fraction) in minutes. And is what we are looking for, in fact. Let's move to the data statements, separately first.

Statement (1) tells us that . If we plug that into our original equation, we can solve for . Sufficient.

Statement (2) looks equivalent, possibly, but it isn't. Along the lines of Statement (1), it would allow us to solve for , but that's not what we are looking for and we don't know the value of . We have three variables and only two equations, so we can't solve completely. (We didn't solve completely in the first statement, because we didn't get the times for R and L individually; we just got the time for Q through fortuitous algebra.) Statement (2) is insufficient.

The correct answer is (A).