Question

Sally can paint a room in 8 hours while it takes steve 7 hours to paint the same room. how long would it take them to paint the room if they worked together?

Answer 1

rate for Sally is 1 room per 8hrs
rate for Steve is 1 room per 7hrs

combined rate:
1/8 + 1/7 = 1/T
7/56 + 8/56 = 1/T
15/56 = 1/T
56/15 = T
3 11/15 = 3 hrs 44 min