posted by kimnlesc on .
If Sally can paint a house in 4 hours, and John can paint the same house in 6 hour, how long will it take for both of them to paint the house together?
Sally can paint 3 houses in 12 hours.
John can paint 2 houses in 12 hours.
Together they can paint 5 houses in 12 hours.
12/5 = 2.4 hours per house
Sally paints a house in four hrs or .25house per hour
John paints house in 6 hrs or one in .166hrs
If they worked together .25+.166= .416 house per hour or,
1/.416= 2.4 hrs per house