GMAT Focus EditionQuantitative ReasoningEasy
A factory produces widgets. The number of widgets produced per hour by machine A is 'x', and by machine B is 'y'. If machine A produces 100 widgets in 5 hours and machine B produces 120 widgets in 4 hours, what is the combined rate of production for both machines working together?
- A20 widgets/hour
- B30 widgets/hour
- C50 widgets/hour
- D40 widgets/hour
Show answer & explanationAnswer & explanation
Correct answer: C. 50 widgets/hour
First, calculate the individual rates: Machine A rate = 100 widgets / 5 hours = 20 widgets/hour. Machine B rate = 120 widgets / 4 hours = 30 widgets/hour. The combined rate is the sum of individual rates: 20 + 30 = 50 widgets/hour.
Why the other options are wrong
- A. This is the rate of machine A only, not the combined rate.
- B. This is the rate of machine B only, not the combined rate.
- D. This might result from an incorrect calculation of one or both rates.
Combined Rate (Work/Production)
When multiple entities work together, their combined rate is the sum of their individual rates, assuming they work independently.
- Individual rates must be calculated first.
- Rates are typically expressed as 'amount per unit time'.
- Combined rate is simply the sum of individual rates.
Memory trick: Add their speeds to get the team's total sprint.