P and Q can do a project in 20 and 12 days respectively. In how many days can they complete 40% of the project if they work together?

Let total work to be done = 60 units

P can complete the work alone in 20 days

=> P's efficiency = $$\frac{60}{20} = 3$$ units/day

Q can complete the work alone in 12 days

=> Q's efficiency = $$\frac{60}{12} = 5$$ units/day

(P + Q)'s 1 day's work = 3 + 5 = 8 units/day

=> 40% of the work = $$\frac{40}{100} \times 60 = 24$$ units

$$\therefore$$ Time taken by them together to complete 40% of the work = $${24}{8} = 3$$ days

=> Ans - (B)