two pipes a and b can fill a cistern in 37 1/2 minutes and 45 minutes respectively. both pipes are opened. the cistern will be filled in just half an hour, if the pipe b is turned off after?

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10 min

two pipes a and b can fill a cistern in 37 1/2 minutes and 45 minutes respectively. both pipes are opened. the cistern will be filled in just half an hour, if the pipe b is turned off after?

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