Question

The formula r=2√5L can be used to approximate the speed r, in mph of a car that left skid marks of length L, in feet. How far will a car skid at 80 mph?

Answer 1

r=2√5L
80=2√5L
40=√5L
sq. both sides
1600=5L
L=320

Answer 2

this is maybe (without exaggeration) the 8th time i have seen this exact same "skid marks" problem. one line class?

Answer 3

oh and look, it is the Math idol judge problem next. where are these coming from?

Answer 4

\[\large r=2\sqrt{5L}\]


\[\large 80=2\sqrt{5L}\]


\[\large \frac{80}{2}=\sqrt{5L}\]


\[\large 40=\sqrt{5L}\]


\[\large 40^2=5L\]


\[\large 1600=5L\]


\[\large \frac{1600}{5}=L\]


\[\large 320=L\]


\[\large L=320\]
So the car will skid 320 ft.