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Problem 4 - Entrance Test

An empty bucket can be filled from one of three water faucets. Faucet A fills 1/4 of the bucket per minute, faucet B fills 1/6 of the bucket per minute, and faucet C fills 1/8 of the bucket per minute. If two of the faucets are used together, which two will fill the bucket the fastest?

Correct: A

Faucet A fills 1/4 of the bucket per minute and faucet B fills 1/6 of the bucket per minute, so together, they would fill 1/4 + 1/6 = 5/12 of the bucket per minute. Faucet A and faucet C would fill 1/4 + 1/8 = 3/8 of the bucket per minute. Faucet B and faucet C would fill 1/6 + 1/8 = 7/24 of the bucket per minute. Faucets A and B are the fastest combination, so the correct answer is A.