Consider two postmen A and B respectively. A is young and can deliver 20 parcels in 3 hours while B is older than A and can deliver only 15 parcels in 4 hours. If the total number of parcels to deliver is 60, how long they will take working together. Choose the correct choice from the following answers: A) 121/12 hours B) 144/36 hours C) 144/25 hours D) 121/25 hours E) 141/25 hours
work done by 1st = 20/3 , work done by 2nd = 15/4 (here work is work/hour)   total work done together = 20/3+15/4 =125/12   time to do 60 unit work(ie, parcels)= 60*12/125 = 144/25   ANSWER:144/25 hours
<result>C</result>
Consider two postmen A and B respectively. A is young and can deliver 20 parcels in 3 hours while B is older than A and can deliver only 15 parcels in 4 hours. If the total number of parcels to deliver is 60, how long they will take working together.