distance=rate*t

needhelpmom

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Joined
Oct 5, 2005
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At a NASCAR race track, the distance per lap is 2 miles. Lou drives his car at a constant rate of 160 miles per hour.

Ralph drives his car at a constant rate of 170 miles per hour. How long will it take before Ralph gains 2 laps in relation to Lou?

do not know how to figure these word problems out and write an equation can you help me
 

ting

Junior Member
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Sep 18, 2005
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87
See if you can make sense of this.

No of laps = distance/2

Distance = rate * time


No. of laps = rate/2 *time

Equate the number of laps done by Ralph in t hours with the number of laps done by Lou in t hours plus 2.


170/2*t = 160/2*t + 2


Solve for t

85t = 80t + 2

5t = 2

t = 2/5

So it takes 2/5 of an hour.

2/5 *60 = 24 minutes.

Check!

Calculate the number of laps each does in 24minutes.


(170 * 24/60)/ 2 = 34


(160 * 24/60)/2 = 32

Edit: Galactus' approach is better! I'll leave this up as an example of how you can over complicate these thing
 

galactus

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Sep 28, 2005
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7,216
Since distance equals rate*time, we must find out how long it takes until Ralph has 4 miles (2 laps) on Lou.

We could write this as:

160t+4=170t, solve for t.

Once you find t, check your answer. Multiply it by 160 and 170, respectively, and see if there is a difference of 4 miles.
 

needhelpmom

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Oct 5, 2005
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Thanks/ yes it makes since to me now.
 
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