It would take one machine 4 hours to complete a large production order and another machine 3 hours to complete the same order. How many hours would it take both machines, working simultaneously at their respective constant rates, to complete the order?
-
A7/12
-
B1 1/2
-
C1 5/7
-
D3 1/2
-
E7
显示答案
正确答案: C