Question 467974: The formula r=2sqrt(5l) can be used to approximate the speed r, in miles per hour, of a car that has left skid marks of length l, in feet. How far will a car skid at 60 mph?
The car will skid ? feet
Answer by Theo(13342)   (Show Source):
You can put this solution on YOUR website! the formula is r = 2 * sqrt (5*l)
r = speed
l = number of feet of skid.
if the car is traveling at 60 miles per hour, then the equation becomes:
60 = 2 * sqrt (5*l)
you want to solve for l.
divide both sides of this equation by 2 to get:
30 = sqrt(5*l)
square both sides of this equation to get:
30^2 = (sqrt(5*l))^2 which becomes:
900 = 5*l
divide both sides of this equation by 5 to get:
180 = l
this means that the car will skid 180 feet.
to confirm this is a good answer, replace r with 60 and l with 180 in the original equation to get:
r = 2 * sqrt(5*l) becomes:
60 = 2 * sqrt(5*180) which becomes:
60 = 2 * sqrt(900) which becomes:
60 = 2 * 30 which becomes:
60 = 60
since the equation is true, then the answer of l = 180 is confirmed as good.
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