MathRevolution wrote:
There is a total of 1,800 pages that needs to be typed. If it takes 90 minutes when a types alone, 45 minutes when b types alone, and 30 minutes when c types alone. How many minutes does it take if 3 of them work together?
A. 10min
B. 12min
C. 15min
D. 18min
E. 20min
The combined rate of typists a, b, and c is:
1800/90 + 1800/45 + 1800/30 = 20 + 40 + 60 = 120 pages per minute.
Thus, when working together, the typists complete the job in 1800/120 = 15 minutes.
Answer:
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