It would take one machine 4 hours to complete a production order and another machine 2 hours to complete the same order

Q. It would take one machine 4 hours to complete a production order and another machine 2 hours to complete the same order. If both machines work simultaneously at their respective constant rates, the time taken to complete the same order is_______________hours.

(A) 2/3

(B) 3/4

(C) 4/3

(D) 7/3

Ans: 4/3

Solution:

Machine X=4 hours

Machine Y=2 hours

In 1 hour X can work=1/4

In 1 hour Y can work=1/2

In 1 hour (X+Y) can work

=1/4+1/2=3/4

(X+Y) together=4/3 hours