A can do a piece of work in 12 days. B can do this work in 16 days. A started the work alone. After how many days should B join him, so that the work is finished in 9 days?

Question: A can do a piece of work in 12 days. B can do this work in 16 days. A started the work alone. After how many days should B join him, so that the work is finished in 9 days?Solution:A's work in 9 days = 9/12 = 3/4. Remaining work = 1 - 3/4 = 1/4.B can do full work in 16 days1/4 portion of work was done by B in (1/4) × 16 = 4 days.∴ B would have joined A after 9 - 4 = 5 days.