Problem-Solving and Data AnalysisVery hardCombined rate of two machines
Problem-Solving and Data Analysis practice question
Machine A can fill 180 bottles in 45 minutes, and Machine B can fill 120 bottles in 40 minutes. Working together at these rates, how many minutes will the two machines take to fill 350 bottles?
Answer: 50
Rates: A fills 4 bottles/min, B fills 3 bottles/min, together 7 bottles/min. 350 ÷ 7 = 50 minutes.
Common wrong answers
- If you answered 85
- 85 adds the two times (45 + 40); working together is faster than either alone.
- If you answered 87.5
- 87.5 divides 350 by 4, using only Machine A's rate.
- If you answered 116.7
- 116.7 divides 350 by 3, using only Machine B's rate.
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