Brajen can paint a wall red in 10 hours while Ballari can whitewash the wall completely in 12 hours. If Brajen and Ballari work alternately for an hour each starting when the wall has just cement on it till when it is completely painted red, how many hours will it take to paint the entire wall red?
LCM of 10 and 12 is 60
In one hour Brajen can do 60/10 =6 units of work
In one hour Ballari can undo 60/12 =-5 units of work
So in 2 hours 1 unit of work is done
In 108 hours 54 units of work is done
In the next hour Brajen does 6 units of work to complete the wall. Â
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