Running at their respective constant rates, machine X takes 2 days longer to produce w widgets than machine Y. At these rates, 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?
4
6
8
10
12
假设W=4
X:干w=4,需要n+2天,每天干4/(n+2)
Y: 干w=4,需要n天,每天干4/n
方程式1:(4/(n+2) + 4/n) *3 = 5
方程式2: 2w=8,8/(4/n+2)) = 选项
此时带入选项ABCDE入方程式2,得到n,再代入方程式1验证,即可知道该选项是否正确。
登录 或 注册 后可以参加讨论