1. Accident Investigation
Example 4
Using Radical Expressions
Accident Investigation
After a car accident, a police officer measures the
length l (in feet) of a car’s skid marks. The expression
gives the car’s speed in miles per hour at the time the brakes were applied.
27l a.
Write the expression in simplest form. b.
The skid marks are 125 feet long. Use the simplified expression to approximate the car’s speed when the brakes were applied.

2. Example 4 SOLUTION = 27l 9 • 3 l a. = • 3l 9 = 3 3l ANSWER
Using Radical Expressions
SOLUTION
Factor using greatest perfect
square factor. =
27l 9 • 3 l a.
Product property of square roots = • 3l 9
Simplify. = 3 3l
ANSWER
In simplest form,
27l = 3
3l . 2

3. The car’s speed was about 58 miles per hour.
Example 4
Using Radical Expressions b. 3 3l = 3 •
125
Substitute 125 for l.
Multiply.
375 3 =
Approximate using a calculator. ≈ 58
ANSWER
The car’s speed was about 58 miles per hour. 3