- A30 days
- B60 days
- C20 days
- D10 days
Step-by-Step Solution
Sum of pair rates = 1/12 + 1/15 + 1/20 = 12/60 = 1/5, which counts each person twice, so P + Q + R = 1/10 per day. P = 1/10 − 1/15 = 1/30, i.e. 30 days.
Answer: A) 30 days
Working in pairs, P and Q finish a job in 12 days, Q and R in 15 days, and R and P in 20 days. How many days would P need working alone?
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