A swimming pool has four faucets. The first can fill the entire pool with water in two days, the second – in three days, the third – in four days, and the last one can fill the pool in 6 hours. How long will it take to fill the pool using all 4 faucets together?

Each faucet's rate of filling is 1 divided by the time it takes alone: 1/48 per hour (2 days), 1/72 per hour (3 days), 1/96 per hour (4 days), and 1/6 per hour (6 hours). Adding these rates together (using a common denominator of 288) gives a combined rate of 61/288 of the pool per hour, so filling the whole pool takes 288/61 hours, which works out to about 4 hours, 43 minutes, and 17 seconds.

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