Machines X and Y run at different constant rates, and machine X can complete a certain job in 9 hours. Machine X worked on the job alone for the first 3 hours and the two machines, working together, then completed the job in 4 more hours. How many hours would it have taken machine Y, working alone, to complete the entire job?
-
A18
-
B $$13\frac{1}{2}$$
-
C $$7\frac{1}{5}$$
-
D $$4\frac{1}{2}$$
-
E $$3\frac{2}{3}$$
显示答案
正确答案: A