Question

Robert can paint a room in 6 hours. Julio can paint a room in 8 hours.how long will it take for the two of them to paint a room together?

Answer 1

Roberto paints 1/6 of a room in 1 hour.
Julio paints1/8 of a room in 1 hour.

Working together, they paint (1/6 + 1/8) = (4/24 + 3/24) = 7/24 room per hour.

The reciprocal unit rate is  24/7 hour per room = 3-3/7 hours per room.