A & B together can complete a work in 30 days. They started work together but after 23 days B left the work and whole work was completed in 33 days. Find the time in which B alone can complete the work.

100 days

A and B does the work in 30 days, it means A also works for 30 days and B also works for the same 30 days.

If B does not work for last 7 days, then that piece of work will be completed by A in 3 days. (after working 30 days)

Therefore,

B’s 7 days work = A's 3 days work

                   A    :     B

Efficiency :   7    :     3   \(\longrightarrow \) 10

Total work  =  Time × Total efficiency = 30 × 10 = 300

B (alone) can finish the work in = \(\frac{300}{3}\) = 100 days