Question 958809
In the time it took you to walk 18 steps, the car traveled (18+126)=144 steps. so the car is traveling 144/18 times as fast as you.
As a ratio: (x=speed of the car) 
144 steps/18 steps=x/4mph Multiply both sides by 4mph (steps cancels out)
(576/18)mph=x
32mph=x ANSWER: The car is traveling 32 mph