Jack usually mows his lawn in three hours. Marilyn can mow the same yard in 5 hours. How much time would it take for them to mow the lawn together?

Answer 1

Jack --> 1/3 yard/hr
Marilyn --> 1/5 yard/hr

together 1/3+1/5 = 5/15+3/15 = 8/15 yard/hr

so 15/8 hr/yard

15/8 hr/yard * 60 min/hr = 112.5 min = 1 hr 52 1/2 minutes