A-A+
Working alone a small pump takes twice as lon
问题详情
Working alone, a small pump takes twice as long as a large pump takes to fill an empty tank. Working together at their respective constant rates, the pumps can fill the tank in 6 hours. How many hours would it take the small pump to fill the tank working alone？
A．8
B．9
C．12
D．15
E．18请帮忙给出正确答案和分析，谢谢！
参考答案
正确答案：E
解析：单独工作时，一个小水泵充满一个空水箱所花的时间是大水泵的两倍。两个水泵保持其各自通常的速度共同工作时，共需花6个小时灌满水箱。若小水泵单独工作时，需花多长时间才能灌满水箱?解：本题的正确答案是(E)。设小水泵需花x小时灌满水箱，则大小泵需花x/2小时灌满小箱，由题意可得：(1/x+2/x)×6=1→x=18
