A, B and C can complete a work in 10, 20 and 30 days respectively. If D can destroy the same work in 15 days. Find the time taken by all of them to complete the whole work.
1
50/7days
2
60/7 days
3
20/3 days
4
40/7 days
5
None of these
A, B and C can complete a work in 10, 20 and 30 days respectively. If D can destroy the same work in 15 days. Find the time taken by all of them to complete the whole work.