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Example 9.87 from Elementary Algebra, 9.6 Solve Equations with Square Roots
Solve Equations with Square Roots: example 9.87
After a car accident, the skid marks for one car measured 190 feet. Use the formula to find the speed of the car before the brakes were applied. Round your answer to the nearest tenth.
Work it out on paper first. Then open the solution one step at a time, and stop as soon as you can finish on your own.
Solution
Step 1. Read the problem. Step 2. Identify what we are looking for. The speed of a car. Step 3. Name what we are looking for. Let s = the speed. Step 4. Translate into an equation by writing the appropriate formula. Substitute the given information. Step 5. Solve the equation. Round to 1 decimal place. Step 6. Check the answer in the problem. Is 67.5 mph a reasonable speed? Yes. Step 7. Answer the question with a complete sentence. The speed of the car was approximately 67.5 miles per hour.
Your turn
The book's Try It right after this example: same idea, new numbers. Only the answer is given.
An accident investigator measured the skid marks of the car. The length of the skid marks was 76 feet. Use the formula to find the speed of the car before the brakes were applied. Round your answer to the nearest tenth.
How did it go?