12/11 Percent Error

​12/11/25 Percent Error Lesson 4.3.6

Learners can....

use the percent error formula to find the percent error, actual amount, or estimated amount of a given scenario

explain the solution method used to solve percent error problems

compare and contrast strategies used for solving problems about percent error with strategies used for solving problems about percent increase or decrease

Math Materials: calculator

By Steven Conway

Match

Match each expression with its estimate. Use percentages you already know or could easily find.

• 25% of 15.8

• 1.2% of 127

• 0.53% of 6

4

1.5

0.03

• 4

• 1.5

• 0.03

Math teammates have something to say

How to determine how much a plant has been overwatered (and the teammates have something to say about that, too)

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Context for next question

You ride the bike to an air pump at a local gas station to check the tire pressure. You find that the tire pressure reads 63 psi. You suspect that this pressure is about 5% too high. You decide to estimate what the pressure should be.

Multiple Choice

Your friend is helping fix the air pressure in your bike tire using the manual for the bike. Use the facts to answer the question

Current Pressure: 63 psi

Pressure is 5% higher than what it should be.

What is the actual pressure stated in the manual and calculated by your friend?

• 3.2 psi

• 6.4 psi

• 57 psi

• 60 psi

Find the measurement error (the difference between the actual amount and what the measurement was)

Divide that by the actual value.

Take that answer and multiply it by 100 to convert the decimal to a percent

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How to calculate percent error

Multiple Choice

The crowd at a sporting event was estimated to be 3,000 people. The venue was outdoors, and before the event, it rained. Once the exact attendance was calculated, only 2,486 people attended. The venue over-estimated. A newspaper wants to know how far off they were. You are trying to help.

What steps do you take to find the percent error?

• Subtract 2,486 from 3,000. Then divide that answer by 2,486. Finally, multiply that answer by 100.

• Divide 2,486 by 3,000. Then you would divide by 3,000. Finally, multiply that answer by 100.

• Add 3,000 and 2,486. Then you would divide by 2,486. Finally, multiply that answer by 100.

• identify the actual vs. estimated values first;

• find the measurement error by subtracting the values, biggest − smallest

• divide measurement error by actual value; and

• multiply by 100 to convert to a percentage

How to solve percent error problems

Multiple Choice

To be labeled as a jumbo egg, the egg is supposed to weigh 2.5 oz. A customer makes the claim that an egg in a jumbo egg carton is 4% smaller than the requirement. What is the weight of the egg?

• 2.1 oz

• 2.4 oz

• 2.6 oz

• 2.9 oz

Multiple Choice

A student estimated that it would take 3 hours to write a book report, but it actually took her 5 hours. What is the percent error for her estimate?

• 3%

• 4%

• 25%

• 40%

Multiple Choice

It took 48 minutes to drive downtown. A navigation app estimated that it would be less than that. If the error was 20%, what was the app’s estimate?

• 14 minutes

• 31.4 minutes

• 38.4 minutes

• 56 minutes

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