The equation [tex]\( s = 2 \sqrt{5x} \)[/tex] can be used to estimate the speed [tex]\( s \)[/tex] of a car (in miles per hour), given the length [tex]\( x \)[/tex] of the tire marks (in feet).

A car traveling at 90 miles per hour came to a sudden stop. According to the equation, how long would the tire marks be for this car?



Answer :

To determine the length of the tire marks [tex]\(x\)[/tex] for a car traveling at 90 miles per hour using the equation [tex]\( s = 2 \sqrt{5x} \)[/tex], we can rearrange the equation to solve for [tex]\(x\)[/tex]. Here’s a step-by-step solution:

1. Write down the given equation and the known speed:
[tex]\[ s = 2 \sqrt{5x} \][/tex]
Given speed, [tex]\( s = 90 \)[/tex] miles per hour.

2. Isolate the square root term by dividing both sides of the equation by 2:
[tex]\[ \frac{s}{2} = \sqrt{5x} \][/tex]
Substitute [tex]\( s = 90 \)[/tex]:
[tex]\[ \frac{90}{2} = \sqrt{5x} \][/tex]
Simplify:
[tex]\[ 45 = \sqrt{5x} \][/tex]

3. Square both sides of the equation to eliminate the square root:
[tex]\[ (45)^2 = (\sqrt{5x})^2 \][/tex]
[tex]\[ 2025 = 5x \][/tex]

4. Solve for [tex]\(x\)[/tex] by dividing both sides of the equation by 5:
[tex]\[ x = \frac{2025}{5} \][/tex]
[tex]\[ x = 405 \][/tex]

Thus, the length of the tire marks would be [tex]\(405\)[/tex] feet.

This detailed, step-by-step solution shows that a car traveling at 90 miles per hour would leave tire marks that are 405 feet long.