| If Steven can mix 20 drinks in 5 minutes, Sue can mix 20 drinks in 10 minutes, and Jack can mix 20 drinks in 15 minutes, how much time will it take all 3 of them working together to mix the 20 drinks? |
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(A) 2 minutes and 44 seconds |
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(B) 2 minutes and 58 seconds |
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(C) 3 minutes and 10 seconds |
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(D) 3 minutes and 26 seconds |
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(E) 4 minutes and 15 seconds The easiest thing to do here is to figure out how many drinks Steven, Sue, and Jack can each mix per minute. If Steven does 20 drinks in 5 minutes, then he does 4 drinks in 1 minute. Sue does 20 drinks in 10 minutes, which is 2 drinks per minute. Jack does 20 drinks in 15 minutes, which is 1.33 drinks per minute. So in a one minute time period 7.33 drinks are made. How long for 20 drinks? Simple algrebra: 7.33x=20, so x=20/7.33, which is 2.73 minutes. (.73 of a minute is roughly 44 seconds, so the answer would be 2 minutes and 44 seconds.) The answer is (A).
source: algebra.com |
