Two machines are sawing wood but due to space limitations only one at a time can operate. Machine A is used for the first shift and the other machine for the second shift, while both work half of the third shift. Machine A can do the job in 12 days if it worked two shifts and Machine B can do the job in 15 days if it worked two shifts. How many days will it take to do the job with current work schedule?
A's productivity is 1/12 per day, 1/24 per half day
B's productivity is 1/15 per day, 1/30 per hafl day
Due to the shifts, A and B each worked half day according to current scedule. Therefore, the total days needed to achieve the same amount of job is 1/ (1/24 + 1/30) = 13.333333333333, approximately 13 days.
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发表于 2008-10-17 01:33:00
