天山6-26 怎么不会算了？

renprince

Q26

Running at their respective constant rates, machine X takes 2 days longer to produce W widgets than machine Y. At these rate, if the two machines together produce 5/4 W widgets in 3 days, how many days would it take machine X alone to produce 2W widgets?

A.4

B.6

C.8

D.10

E.12

答案是E， 可是我算了半天都是C。 谁能告诉我答案是怎么算出来的，谢谢！

luoye1

这题我也算错了

assfgrtrtr

(5/4)/(1/x+1/(x+2))=3==>x=6,x=5/4

2/(1/6)=12

设Xmachine X天完成，Ymachine X+2天完成，效率分别是1/x,1/x+2

xiongxiong88

楼主强,顶一下!!