Joe can paint a garage in 24 hours, and Bobby can paint the same garage in 12 hours. The two boys and their father can paint the garage in 4 hours. How long would it take the father to paint the garage?
+23246 Joe's rate: 1 garage every 24 hours = 1/24
Bobby's rate: 1 garage every 12 hours = 1/12
Father's rate: 1 garage every 4 hours = 1/4
time: t
(rate)·(time) + (rate)·(time) + (rate)·(time) = 1 job completed
(1/24)·t + (1/12)·t + (1/4)·t = 1
t + 2t + 6t = 24 (multiply by 24)
9t = 24
t = 24/9
t = 2 2/3 hrs = 2 hrs 40 mins.
