pre calc homework question

Question

Police use the formula:

v=√20L

to estimate the speed of a car, v, in miles per hour, based on the length, L, in feet, of its skid marks when suddenly braking on a dry, asphalt road. At the scene of an accident, a police officer measures a car's skid marks to be 210 feet long. Approximately how fast was the car traveling? Round your answer to the nearest tenth (one decimal place) of a unit.

Answer: The car was traveling at approximately  miles per hour.

Answer 1

If V = sqrt(20) * L then V=sqrt (20) * 210 = 89.4 mph

If V=sqrt(20L) then V=sqrt(20*210) = 64.8 mph