Using a Graphic Organizer to Calculate Sales Tax
Lesson 1 of 16
Objective: SWBAT use a graphic organizer to organize their thinking in order to calculate tax applied to items purchased.
Teacher Guided Notes: In order for students to successfully calculate tax, students will need a strong number sense background. Students will convert percentages to decimals, estimate to the nearest hundredth place, multiply decimals, add decimals, and identify values of decimals. Students should use their knowledge gained from 6.NS.B.3 to help calculate the tax and increased amount. In future lessons, we will learn to model the steps using bar diagrams, and tables to calculate tax.
It is important to tie in real world scenarios in this lesson so that students have an understanding of how important it is to determine the sales tax on items purchased. Students must understand the relationship between the amount purchased and the amount of the tax. Some students may not have a clear understanding that the percentage of tax in their state will not change, but the amount will in relationship to the item purchased. For example, the state of Ohio is up to 7% sales tax, if you purchase a candy bar, this will be a minimal increase to the total amount needed to purchase the candy bar, but if you purchase an automobile or a home, the total amount needed to purchase the home or car will increase drastically. Why? In this lesson we will discuss the procedures in finding sales tax. In a future lesson we will discuss sales tax across the country, how that affects the cost of living, which state has the least percentage of sales tax, and does that affect the population of that state.
Opener : Whole group Discussion
Open this lesson with a whole group discussion from the previous day’s lesson over calculating discount. Discuss the strategies students used. Address common mistakes made. One main common mistake students make is subtracting the percentage, and not finding the discount. One other common mistake for students to make is finding the discount and using this as the sale price. Discuss how using the graphic organizer enabled them to organize their thinking in order to solve for the discount and find the sale price. Students should have kept note over the mistakes that they made. Allow the students to discuss these mistakes and double check their work.
bell ringer: Hand each student the bell ringer as they enter the room. Have students work on the problems 1, 4, and 7 for 10 minutes. Students will use mathematical practice 1, 2, 4 and 6. My students have assigned seats for their I.T.T seats, once again this is their Individual Think Time seats. Students will grapple with the problem for 10 minutes on their own. During this time students may use a variety of strategies to calculate the tax. Students should explain their thinking, record their work, and articulate the strategy they chose in order to solve the problem.
Wait to give your students the graphic organizer until the student activity. After students have had the opportunity to organize their thoughts, think quantitatively, and/or abstractly, try different methods, reorganize their thoughts, and attempt to solve the problem with accuracy, allow the students to pair up with another student or group of students to compare their thinking and results.
Students will be in P.U.T seats. This is pair up time. Students will use MP 3 during this time. Students should defend their thinking with their peers, critique the work of others, and correct mistakes as a result of the mathematical discussions. Allow students 10 minutes during P.U.T. During this time while you walk the room checking for understanding you are looking for students who are able to calculate the tax, and new price. Students who have little to no understanding will attempt to solve the problem by adding the percent to the original cost.
The graphic organizer will help with this misconception. Use the opening discussion to help guide student thinking. Students should use their understanding of discounts toward the understanding of calculating tax. It is often underestimated the power of isolating discount meaning an amount off, and tax an amount added. The meat of the discussion will be for students to understand what the percent means, what is the relationship of the percent to the original cost? How will that information help you solve the problem? Students should also understand that finding the tax is different than finding the new cost. The tax is the amount added to the original cost, the new cost is the price after the tax is added. I would start student thinking with placing them in a personal situation. Every student has been able to buy an item once in their life with their own money. Ask them to share their experience.
What was the price of the item?
Did you pay the price tag amount?
If not, was it more or less? Why?
Student Activity: After students have had the opportunity to grapple through the problem, give them the graphic organizer. Allow students to use their work accomplished during the bell ringer and adjust thinking using the graphic organizer. Allow students 10 minutes to use the graphic organizer. During this time assess if the graphic organizer reorganizes student thinking. The graphic organizer will help students who have little understanding gain starting points, isolate the stages of the process, and help students build understanding of the process in order to build other strategies to calculate tax. For students who have a strong understanding calculating sales tax, have these students work on numbers 3, 5, 6, and 8. Students who may struggle will need the full 10 minutes to use the graphic organizer to help them go step by step in solving for sales tax.
Closing: Due to the time of this lesson, we will bypass the whole group discussion. Open your next day lesson with the whole group discussion. During the whole group discussion compare the two graphic organizers and the processes from both. Talk about the difference in discount and tax. Discuss ways in which discounts will be taken. Students should identify, percentages off, amounts off, and even a combination of both.
Where do we encounter discounts?
What time of the year are discounts (sales) most prevalent? Why?
Does this help sales?
Will the sales tax increase during this time? Why or why not?
In this closing, use your Smartboard, document camera, white board, or chalk board to go over the graphic organizer. Have students check their work as you go over each step of the graphic organizer. If students make mistakes, encourage them to correct their mistakes, and also keep note of the mistakes they made to talk about them during the whole group discussion during the next day lesson opener.
Have students complete 3, 5, 6, and 8 from the bell ringer/homework sheet. Those students who feel they are still struggling, allow them to use the graphic organizer to help them through the process. For students who have a strong understanding have them complete number 9 and 10. This will be the opener for the next day's lesson. The students with strong understanding will become the experts of the room. The other students will be able to consult with them, gain understanding through peer to peer tutoring.