danlew wrote:

Sam can repair a machine in 15 days and Ross can repair the same machine in 25 days. If they decide to repair the machine on alternate days, with Ross on the first day, followed by Sam on the second day and so on till the repair is completed, how many days do they take to complete the repair work.

A) 17

B) 18

C) 19

D) 20

E) 21

Let the total work be 75 units.

Efficiency of Sam = 5 units/day

Efficiency of Ross = 3 units/day

Since they work alone on alternate days then they complete 8 units of work in 2 days..

That is they complete 72 units of work in 18 days (Simply multiply by 9)

After that 3 units of work is left which Ross completes in 1 days...

So, the work will be completed in 19 days, Answer must be (C) 19 days
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Thanks and Regards

Abhishek....

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