数学一道 谢谢了

genius1824

Machines X and Y work at their respective constant rates.How many more hours does it take machine Y, working alone, to fill a production order of a certain size than it takes machine X, working alone?


(1) Machines X and Y, working together, fill a production order of this size in two-thirds the time that machine X, working alone, does.



(2) Machine Y, working alone, fills a production order of this size in twice the time that machine X, working alone, does   条件1和2是说谁是谁的几倍呀  没有看懂  帮我翻译一下吧  

kronorrt

(1) x和y的rate是x的2/3
(2) y rate是x的兩倍

778879147

条件一：1/(1/x+1/y)=2/3*1/x  显然不成立
条件二：1/y=2/x 也不成立
综上，1+2合适，两个未知数，2个方程，可解。选C
不知道对不对，请大N指正

applemay

How many more hours does it take machine Y 条件只有比例没有具体时间 所以D

778879147

E吧。。两个式子都只能推出y的效率是x的效率的一半。。