The formula r =2 sqrt.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?

Answer 1

the way you typed it would be

r = (2√5) L

or did you mean
r = 2√(5L)

major difference between the 2 formulas,
please clarify.

Answer 2

2√(5L) = 60
√(5L) = 30
5L = 900
L = 180