A and B can do a piece of work in 21 and 24 days respectively.They start the work together and after some days, A leaves and B completes the rest of the task in 9 days. After how many days did A leave?
Q1. A and B can do a piece of work in 21 and 24 days respectively.They start the work together and after some days, A leaves and B completes the rest of the task in 9 days. After how many days did A leave?
Answer: 7
Explanation: B completes 9/24 = 3/8 alone; remaining 5/8 done together at rate 1/21+1/24 = 15/168; time = (5/8)/(15/168) = 7 days.