Car LapsDate: 01/26/2001 at 14:11:46 From: Andy Chang Subject: Distance and Rate On a race track, one car travels five laps a minute and another car travels eight laps a minute. How long will it be before the second car laps the first? Date: 01/26/2001 at 16:04:49 From: Doctor Greenie Subject: Re: Distance and Rate Hi, Andy - You can answer this question using algebra, but it's almost easier in this case to answer just by some careful analysis. By using algebra: In x minutes, the number of laps traveled by the first car is 5x, and the number of laps traveled by the second car is 8x. We want to find the value of x for which the second car has traveled one lap farther than the first: 8x = 5x + 1 This is an elementary algebra equation that gives us the answer x = 1/3 minute. By using careful analysis: The second car goes 8 laps a minute while the first car goes only five laps in that same minute. The second car therefore goes three laps farther every minute, so it laps the other car three times each minute. So it laps the first car every 1/3 minute, and the first time it laps the first car is after 1/3 of a minute, or 20 seconds. - Doctor Greenie, The Math Forum http://mathforum.org/dr.math/ |
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