A work can be completed by P and Q in 12 days, Q and R in 15 days, R and P in 20 days. In how many days P alone can complete the work ?
A work can be completed by P and Q in 12 days, Q and R in 15 days, R and P in 20 days. In how many days P alone can complete the work ?
[A]10 days
[B]20 days
[C]30 days
[D]60 days
30 days
(P + Q)’s 1 day’s work 
(Q + R)’s 1 day’s work 
(R + P)’s 1 day’s work 
On adding,
2(P + Q + R)’s 1 day’s work
∴ (P + Q + R)’s 1 day’s work 
∴ P’s 1 day’s work
∴ P alone will complete the work in 30 days.
Hence option [C] is correct answer.
