A manufacture packages soap powder in containers of three different sizes. The amount of soap powder in a full large container could fill exactly 3 of the medium containers or exactly 5 of the small containers. If an equal number of small and large containers are to be filled with the amount of soap powder that would fill 90 medium containers, how many small containers will be filled?
E.55

A.25
B.27
C.30
D.45

【参考答案】

A
解析：一名制造商把洗衣粉装入三种不同尺寸的容器中。装满的大容器中的洗衣粉的量可以装满3个中型容器或5个小容器中，若相同数目的小容器和大容器所盛的洗衣粉能装满90个中型容器，问小容器的数目是多少?
解：本题的正确答案是(A)。设装满的大容器中的洗衣粉量为a，则中型容器中可以盛洗衣粉量为1/3 a，而小容器中可以盛1/5 a，设可以装入90个中型容器中的洗衣粉可以放入n个大容器和n个小容器中，则由题义可得到下面的等式：n×(a+1/5 a)=90×1/3 a => n=25