Question 1150876
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Since the rate of pipe A is twice that of pipe B, when the two work together pipe A does 2/3 of the job and pipe B does 1/3 of the job.<br>
It takes the two together 6 hours to fill the tank.<br>
So in those 6 hours that it takes the two pipes together to fill the tank, pipe B fills 1/3 of the tank.<br>
And if pipe B fills 1/3 of the tank in 6 hours, it will take it 18 hours to fill the whole tank alone.<br>