Answer
Speed of the car is $40\;mph$.
Work Step by Step
The formula for the speed is
$s=\sqrt{30fd}$
The given values are
Length of the skid marks $d=120\; feet$
Coefficient of friction $f=0.444$
Substitute all values into the formula.
$\Rightarrow s=\sqrt{30(0.444)(120)}$
Simplify.
$\Rightarrow s=\sqrt{1598.4}$
Use calculator.
$\Rightarrow s=39.9799949975$.
Approximate value.
$\Rightarrow s=40\;mph$.
