Question 784474
the 1st can do 1/3 of the job in 1 hr.
the 2nd can do 1/5 of the job in 1 hr.
1/3 + 1/5
=5/15 + 3/15 = 8/15 job done together in 1 hr
15/8 = 1 7/8 hrs to finish.
.
Ed