Percent Change and Percent Error Introduction

Percent Change & Percent Error

Percent Change Equation

• change = percent change x original

• change IS NOT the same as percent change

Multiple Choice

The original quantity is 10 and the new quantity is 13. Is it an increase or a decrease?

• Increase

• Decrease

Multiple Choice

The original quantity is 10 and the new quantity is 13. What is the change?

• 3

• 10

• 13

• 23

The original quantity is 10 and the new quantity is 13. What is the PERCENT change?

• change = percent change x original

• 3 = p x 10

• What number is NOT included in the equation?

• Why not?

Multiple Choice

We need to solve for p. How do you solve 3 = p x 10?

• $$p=3\div10$$

• $$p=10\div3$$
  

• $$p=3\times10$$
  

• $$p=10\times3$$

Solve 3 = p x 10

• Divide by 10

• 3 / 10 = 0.3

• p=0.3 (Change this to a PERCENT %)

Multiple Choice

What is 0.3 as a percent?

• 0.03%

• 0.3%

• 3%

• 30%

Summary: The original quanitity is 10 and the new quantity is 13. What is the percent change? Is it an increase or a decrease?

• Step 1: Find the change: 13-10=3

• Step 2: Find the PERCENT change: 3/10=0.3

• Step 3: Change this to percent: 0.3x100=30%

• Answer: 30% increase

Practice Round 1

Multiple Choice

The original quantity is 5 and the new quantity is 3. What is the PERCENT change? Remember: change = percent change x original

• 0.4%

• 2%

• 40%

• 66%

Multiple Choice

At noon, a tank contained 10 cm of water. After several hours, it contained 7 cm of water. What is the percent decrease of water in the tank?

• 0.3%

• 3%

• 30%

• 42%

Multiple Choice

Craig likes to collect vinyl records. Last year he had 10 records in his collection. Now he has 12 records. What is the percent increase of his collection?

• 0.2%

• 2%

• 16%

• 20%

Multiple Choice

Carl bought an airline ticket for $375. Two weeks ago, the cost of the flight was $300. What is the percent increase?

• 0.25%

• 20%

• 25%

• 75%

Percent Error Equation

• change = percent change x original

• A little bit different now:

• error = percent error x actual

• Error is the difference (you will subtract)

• "Actual" is what the quantity is

Multiple Choice

Rihanna has a container with a volume of 1.5 liters. She estimates the volume to be 2.1 liters. What is the ERROR in her calculation?

• Subtract 2.1 - 1.5 = 0.6

• Add 1.5 + 2.1 = 3.6

Multiple Choice

Rihanna has a container with a volume of 1.5 liters. She estimates the volume to be 2.1 liters. The error is 0.6 liters. Which number represents the actual?

• 1.5

• 2.1

• 0.6

Open Ended

Rihanna has a container with a volume of 1.5 liters. She estimates the volume to be 2.1 liters. The error is 0.6 liters.

Set up the equation.

error = percent error x actual.

The correct equation is:

0.6 = p x 1.5

• 0.6 is the ERROR, or change (2.1-0.5=0.6)

• p is the percent error

• 1.5 is the actual

Multiple Choice

To solve the equation 0.6 = p x 1.5, _______

• Divide 1.5 / 0.6

• Divide 0.6 / 1.5

Multiple Choice

Change your decimal to a percent. What is the final answer?

• 0.4

• 0.4 %

• 40

• 40 %

Practice Round 2

Multiple Choice

Billie Eilish has a container with a volume of 5 ounces. She estimates the volume to be 12 ounces. What is the percent error?

• 7%

• 14%

• 100%

• 140%

Open Ended

Billie's percent error is 140%. What does this mean?

Multiple Choice

Melissa estimated that she would read 200 pages last week. She read 260 pages. What is the percent error of Melissa's estimate?

• 0.3%

• 23%

• 30%

• 60%