Amit can complete a work in 25 days and Punit can complete the same work in 20 days. Punit alone worked at it for 10 days and then left the work. In how many days will Amit alone complete the remaining work?

Let total work to be done = 100 units

Amit can complete the work in 25 days, => Amit's efficiency = $$\frac{100}{25}=4$$ units/day

Similarly, Punit's efficiency = $$\frac{100}{20}=5$$ units/day

Work done by Punit alone in 10 days = $$5\times10=50$$ units

=> Work left = $$100-50=50$$ units

$$\therefore$$ Time taken by Amit alone to finish the remaining work = $$\frac{50}{4}=12\frac{1}{2}$$ days

=> Ans - (B)