GMAT Focus EditionQuantitative ReasoningEasy
A production line has two machines, M1 and M2. M1 can produce 150 units in 3 hours. M2 can produce 200 units in 4 hours. If both machines work together, how many hours will it take to produce a total of 750 units?
- A12 hours
- B9 hours
- C8 hours
- D10 hours
Show answer & explanationAnswer & explanation
Correct answer: B. 9 hours
First, calculate the individual rates of M1 and M2. Then, sum their rates to find the combined rate. Finally, divide the total units required by the combined rate to find the time.
Why the other options are wrong
- A. This might result from miscalculating the combined rate or incorrectly setting up the final division.
- C. This might result from calculation errors in individual rates or combined rate.
- D. This could be an error if only one machine's rate was used for part of the calculation.
Combined Work Rate
The rate at which multiple entities complete a task when working together, calculated by summing their individual rates.
- Individual rates are typically expressed as 'units per time' or '1/time to complete'.
- Combined rate = Sum of individual rates.
- Time to complete = Total work / Combined rate.
Memory trick: Teamwork makes the dream work (faster).