Brain Teasers
Painting a Room
A man can paint a room in four hours, and another man can paint the room in two hours. How long would it take if they worked together?
Answer
80 minutes.Man A can paint a room in 2 h:
1 room/2 hours
Man B can paint a room in 4 h:
1 room/4 hours
Add the times together with the lowest common denominator of 4:
2/4 + 1/4 = 3 rooms/4 hours
We know how long it takes to do three rooms, but we want to know how long it would take to paint one:
3 divided by 3 = 1
4 divided by 3 = 1.333... or 1 1/3 h
1 1/3 h = 80 minutes
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