SOLUTION: Officer Franklin's radar gun stops working in the middle of the day. As a vehicle passes by him he starts a stop watch. As the vehicle passes the bridge one half of a mile away, he

Question 1084718: Officer Franklin's radar gun stops working in the middle of the day. As a vehicle passes by him he starts a stop watch. As the vehicle passes the bridge one half of a mile away, he records the time as 30 seconds, or 1/120 hours. Explain how he could use this information to determine the speed of the car and its location. Write an equation to represent the situation. Is the car speeding? How do you know?
Answer by jim_thompson5910(35256) (Show Source): You can put this solution on YOUR website!
Let r = rate (or speed) of the car in miles per hour.

distance = rate*time
d = r*t
r = d/t

The equation we'll use is r = d/t. Plug in the distance of d = 1/2 = 0.5 miles and t = 1/120 = 0.00833333333333 (approximate) hours to get

r = d/t
r = 0.5/0.00833333333333
r = 60.000000000024
which rounds to 60

If we use fractions instead of decimal approximations, we land on r = 60 exactly without any rounding errors.

The car's speed is 60 mph.

Is the car speeding? Well that depends on the posted speed limit. That information isn't given in the problem, so it's impossible to say if the car is speeding or not.
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