The formula s = √18d can be used to find the speed s of a car in miles per
hour when the car needs d feet to come to a complete stop after stepping
on the brakes. If it took a car 25 feet to come to a complete stop after
stepping on the brakes, estimate the speed of the car. Truncate the value
of √18d, when d = 25, to the tenths place.
Substitute d=25 to the formula and use a calculator to evaluate: s=18(25 s=450 s~21,2132... Truncated to the tenths place, we have: s~21.2 miles per hour.
