Question

A firm advertises for workers to address envelopes. Priscilla says she will work 100 hours. Herb will work for 80 hours. If each can address 10,000 envelopes in the time they work, how long would it take them to address 10,000 envelopes if they work together?

Answer 1

Combined work problems
job/time + job/time = job/ total time

(1/80) + (1/100) = 1/T
(10/800) + (8/800) = 1/T
18/800 = 1/T
800/18 = T
44.44 hrs = T