Bob can wash a car in 6 minutes. Bill can wash a car in 8 minutes. How long will it take if Bob and Bill wash a car together?

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Answer 1 · 2015-09-10T02:15:00

#24/7"minutes"#

Bob can wash a car in 6 minutes. So in one minute washes #"1/6"# of a car.

Bill the same washes #"1/8"# of a car in a minute. Both wash the car in #1/x# minutes. But

#1/6+1/8=1/x=> 24x*1/6+24x*1/8=24x*1/x=>4x+3x=24=> 7x=24=>x=24/7"minutes"#