
Elementary Math Fractions, Percentages, Word Problems, Equations, Inequations, Factorization, Expansion 
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December 12th, 2015, 09:52 PM  #1 
Senior Member Joined: Oct 2013 From: Far far away Posts: 422 Thanks: 18  Drag racers
Two professional drag racers are speeding down a 1/4 mile track. If the lead driver is travelinvg 1.738 feet for every 1.670 feet that the trailing car travels,and if the trailing car is going 198 miles per hour, how fast in miles per hour is the lead car traveling? My attempt... 1.738/1.670 = x/198 So the lead car's speed(x) = 206 miles per hour Am I correct? Thanks 
December 13th, 2015, 04:43 AM  #2 
Math Team Joined: Jan 2015 From: Alabama Posts: 2,822 Thanks: 750 
Another way to think about it: If the trailing car goes 1.670 ft in t seconds, then his speed is 1.670/t feet per second. That is the same as 1.670/t= C(198 miles per hour) where "C" is the conversion factor from "miles per hour" to "feet per second". In the same time, the lead car goes 1.738 feet so 1.738/t= Cv where v is now the speed, in miles per hour, of the lead car. Dividing the second equation by the first, both "t" and "C" cancel leaving 1.738/1.670= v/198 which gives your solution.


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