Question

If x y z can do a work in 10 12 15 days respectively then x y z together can do the same work in

Answer 1

Time taken by A to do work alone = 10 days
Time taken by B to do work alone = 12 days
Time taken by C to do work alone = 15 days.

Now,
Part of work done by A in one day = 1/10
Part of work done by B in one day = 1/12
Part of work done by C in one day = 1/15

Now,
When A,B & C work together then the part of work done =
1/10+1/12+1/15
= 6/60 + 5/12 + 4/60
= 15/60

Now,
15/60 is the part of work done by A,B & C together in one day

So, clearly
60/15 = 4 days will be taken by all A,B & C to complete the work together.

Answer 2

Total work of x, y, and z = 1/10 + 1/12 + 1/15
= 6 + 5 + 4 / 60
= 4/15 = 15 / 4
= 15/4 days