Two pipes, A and B can fill an empty cistern in 20 min and 40 min, respectively. Both the pipes are opened together, and after some time, pipe A is closed. If the cistern gets filled in 30 min, then for how long was pipe A kept open?
5 min
The correct answer is 5 min.
In problems where participants work for different durations, the total work is the sum of the work done by each participant during their respective working times. This sum usually equals '1' if one complete task is done. These problems often require setting up a linear equation based on the total work completed, similar to how we solved for the time Pipe A was open in this question.
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Important Questions from Pipe and Cistern
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The compound interest on Rs. 64,000 for 3 years, compounded annually at 7.5% p.a. is
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