Question

B can complete a work in 6 days. A alone can do it in 10 days. If both work together how many days they will take to complete the work?

Answer 1

B does 1/6th of the work per day. A does 1/10th. Together, they do:

1/10 + 1/6=3/30 + 5/30=8/30=4/15

1/ 4/15=15/4 days working together.