Work Problem

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Work Problem

by sunsphere314 » Wed Sep 07, 2011 12:54 pm
Would someone please help me with this question?

Cars are entering the parking lot of a suburban shopping mall at the rate of one car every three seconds, and leaving at the rate of one car every seven seconds. The parking lot is filling at a rate of approximately one car every

a) 6 seconds b) 5 & 1/3 seconds c) 5 & 1/4 seconds d) 3 & 3/7 seconds e) 2 & 1/10 seconds

Thank you!
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by GMATGuruNY » Wed Sep 07, 2011 1:08 pm
sunsphere314 wrote:Would someone please help me with this question?

Cars are entering the parking lot of a suburban shopping mall at the rate of one car every three seconds, and leaving at the rate of one car every seven seconds. The parking lot is filling at a rate of approximately one car every

a) 6 seconds b) 5 & 1/3 seconds c) 5 & 1/4 seconds d) 3 & 3/7 seconds e) 2 & 1/10 seconds

Thank you!
Let time = 21 seconds.
Since one car enters every 3 seconds, number of cars entering = 21/3 = 7.
Since one car leaves every 7 seconds, number of cars leaving = 21/7 = 3.
Net increase in the number of cars = number entering - number leaving = 7-3 = 4.
Thus, filling rate = 4 cars per 21 seconds = 1 car per 21/4 seconds.

The correct answer is C.
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by navami » Thu Sep 08, 2011 5:30 am
5-1/4
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