Question

Jack can paint the bedroom in 12 hours, and Rick can do it in 10 hours. They work together for three hours. How long will it take Jack to finish the job alone?

Answer 1

5 hours 24 minutes.

Explanation:

If Jack can paint the room in 12 hours, then in 3 hours he will have painted `1/4` of the room.

Rick can do it in 10, so in 3 hours he will have painted `3/10` of the room.

`1/4 + 3/10 = 11/20`

Jack has to paint `1-11/20 = 9/20` of the room by himself.

`9/20*12 = 27/5 = 5.4 hr`