Introduction of the concept: Working with percentage increase/decrease. Prior knowledge of multiplication and division is required.
Materials needed: Textbook, worksheets, price tags with percents off
Standards: Numbers and Operations
Illinois Standards: 6.C.2a, 6.C.2b, 6.C.3a, 6.C.3b
Lesson objectives:
– Students will demonstrate how to calculate percent increases
– Students will demonstrate how to calculate percent decreases
– Students will demonstrate the ability to calculate percent increases and decreases in real life situations
Class set up: This activity should be done as a whole group lesson
Anticipatory set: So your favorite music store is featuring 30% off all CD’s! Plus all portable CD players are 15% off! And as a bonus, you get 10% off your total purchase! You need a new Disc-man and would love to have a couple new discs. You brought $35. Is it enough for what you want?
Procedure:
1) Review multiplication and division of whole numbers and decimals
2) Introduce real life examples of using percent decreases (ex. A $15 CD that’s 30% off would be $10.50)
3) Discuss real life examples of using percent increases (ex. If a CD store tags on a 45% markup before putting an item up for sale, a $15 CD actually only cost the store $8.25)
4) Discuss procedures for calculating percent decrease (there are multiple methods)
– Decreasing a number by multiplying it by 100% less the percent decrease
– Decreasing a number by multiplying it by a percent and subtracting the decrease from the original amount
5) Discuss procedures for calculating percent increase (there are multiple methods)
– Increasing a number by multiplying it by a percent and adding the increase to the original amount
– Increasing a number by multiplying it by 100% plus the percent increase
6) Work on example problems in class (using the anticipatory set example) Allow students to attempt to discover the best or easiest methods to calculate these problems on their own
7) Go over the sample problems and discuss which methods worked best and why. Remind students that there are multiple methods, so what works best for one student may not be as easy for another
8) Hand each student out a number of price tags at random. Tell the students they must determine the final price of these items based on the percent increase or decrease listed on the price tags.
9) As homework, students will find examples of percent increases and decreases in sales papers/catalogs, and determine the price for at least 6 items. They will bring in the sales papers/catalogs the next day along with their work.
During the procedure: After the students try the problems on their own, the teacher will take the students through the practice problems, explaining each step if needed.
Checking for understanding: Once the basic concept is explained, students will work on problems in class. The teacher will observe the work of each student to ensure understanding.
Assessment: Students will demonstrate calculation of percent increase and decrease in class. The teacher can observe the level of success with each student as they work on each problem. Review homework and a section review quiz will provide further assessment
Conclusion: Showing that calculation of percent increases and decreases is a part of every day life.
