Students are given a collection of statements that are incorrect. Their task is to construct arguments about why the statements are flawed and then correct the flawed statements.
- Percent change is a rate of change of an original amount.
- In two situations with the same percent change but different original amounts, the percent amount will be different because the percent amount depends directly on the original amount. For example: 50% of 20 is 10. 50% of 10 is 5.
- Similarly, in two situations with the same amount of increase but different original amounts, the percent change of each amount is different. For example: Suppose two amounts increase by $5. If one original amount is $20, the increase is 25%. If the other original amount is $25, the increase is 20%.
Goals and Learning Objectives
- Identify errors in reasoning in percent situations.
- Use examples to explain why the reasoning is incorrect.