Julie paints a house in 4 hours and Ken paints the same house in 5 hours. If they work together, they can paint the house in how many hours and minutes?

Work rates add linearly, so that:


1/4 +1/5 = 1/t
t=(4*5)/(4+5)=20/9


t= 2 2/9 hours



converting the fraction to minutes:
(2/9)*60= 13 1/3

1/3 of a minute is 20 sec, so...that the time is 2 hrs, 13 minutes and 20 sec