Sam can sort 4000 pieces of mail in 5 hours. With a co-worker they can sort 4000 pieces of mail in 3 hours. How long will it take his co-worker to sort 2000 pieces of mail.

Answer 1

consider 4000 pieces one "job". The classic work problem now becomes

1/5 + 1/x = 1/3
x = 15/2

So, he can sort 2000 mails (1/2 job) in 15/4 hour