Working alone, pump A can empty a pool in $3$ hours. Working alone, pump B can empty the same pool in $2$ hours. Working together, how many minutes will it take pump A and pump B to empty the pool?

Correct answer marked below

Correct

108

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Comments

TamJun 23

Wait, I got 1.2 hours and then multiplied by 60... is that right? I got 72 but that feels too clean for a GMAT question lol

RajdeepAug 27

Easy one but the trap is forgetting to convert hours to minutes at the end. Almost picked 1.2 lol

RewantMay 9

Can someone explain why we use 1/3 + 1/2? I always get confused on these combined work problems

EnioluwafeApr 14

Got 72, these sub-500 work rate ones are a nice confidence boost before the harder ones 😅

What this question tests

Your ability to combine individual work rates, usually by working with the fraction of a job completed per unit of time.

Adding the times instead of the rates, or forgetting to take the reciprocal when combining rates.

Working alone, pump A can empty a pool in 333 hours. Working alone, pump B can empty the same pool in 222 hours. Working together, how many minutes will it take pump A and pump B to empty the pool?