Question

P and Q can do a work in 12 days, Q and R in 15 days, R and P in 20 days. Find in what time P will do it alone?​

Answer 1

Step-by-step explanation:

1/p + 1/q = 1/12

1/q + 1/r = 1/15

1/r + 1/p = 1/20

add the above equations

2(1/p + 1/q +1/r) = 1/12 + 1/15 + 1/20

1/p + 1/q + 1/r = 1/3

1/p + 1/15 = 1/3

1/p = 1/3 - 1/15 = 4/15

P takes 15/4 days to do the work alone.