A can do 1/3 of a work in 5 days and B can do 2/5 of the work in 10 days. In how many days both A and B together can do the work?
Answer: C
A can do the full work in \(5 \times 3 = 15\) days. B can do the full work in \(10 \times 5/2 = 25\) days. A's 1 day work = 1/15. B's 1 day work = 1/25. Together, their 1 day work = \(1/15 + 1/25 = (5+3)/75 = 8/75\). They will take 75/8 = 9 3/8 days.