Pawan and Qureshi can individually complete a certain task in 5 hours and 15 hours, respectively. Pawan begins the task at 9:00
a.m., and they work alternately for one hour each, with Pawan starting first. At what time will the task be completed?

ATQ, Let total work be 15 units {LCM of 5 and 15} Efficiency of ‘Pawan’ = (15/5) = 3 units/hour Eiciency of ‘Qureshi’ = (15/15) = 1 units/hour Work done by ‘Pawan’ and ‘Qureshi’ in every 2 hours = (3 + 1) = 4 units So, work done in irst 6 hours = 4 × 3 = 12 units Remaining work = (15 – 12) = 3 units Since, ‘Pawan’ is next in line to do the work, he will finish the remaining work in (3/3) = 1 hour So, total time taken by ‘Pawan’ and ‘Qureshi’ to do the work together = 1 + 6 = 7 hours Therefore, the work will be inished at 4:00 p.m. i.e., 7 hours after ‘Pawan’ started working.