# Commission, tax, tips, and other Gratuities

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## Objective

SWBAT compute gratuity, tax, tip, and commission

#### Big Idea

students use bar models and numeric expressions to problem solve using tax, tip, gratuities and commission

## Do Now

10 minutes

Students enter silently according to the Daily Entrance Routine. Their Do Now assignment is faced down, and students are asked NOT to turn the paper over. They must write their names on the back side of this paper without turning it over. As we continue working within this percents unit, we also continue to start class with conversion sprints. These sprints are built from materials available on the EngageNY state website developed to support the common core curriculum. For more resources within this module (Percent and Proportional Relationships) visit this link.

Students have 5 minutes to complete as many problems as possible. To continue motivating all students I continue to stagger the awards given so that students have incremental goals. Achievement points are awarded as follows:

• 1 achievement point if they completed an entire column
• 2 achievement points if they completed an entire column and 80% or more of the answers were correct
• 3 achievement points if they completed BOTH columns AND 80% of the answers of more were correct
• 4 achievement points if they completed BOTH columns and ALL of the answers were correct

This strategy worked best because it challenges students at different levels. Even the students who struggled academically the most with these conversions pushed themselves to complete an entire column and see progress. In the last 4 – 5 minutes of this section, I elect a a student to cold call the rest to give the answers and write them on the board while I am walking around awarding achievement points to students. Students are then asked to put their sprints away after all answers are reviewed and class notes are distributed.

## Class Notes

10 minutes

Students must first fill out the heading and copy the aim at the top of their notes. The class notes resources I have attached in this section also include a teacher copy of the notes. Any red fonts indicate notes that are to be written on the board for students to copy. We begin by copying the definition of commission. I anticipate a common misconception with commission, tip and gratuities. Students must understand that a commission is a piece that an employee earns for selling a product, while a tip or gratuity could be added to an original amount. This distinction must be made early on and reviewed as much as possible through work problem examples.

After copying the definition of commission I model using bar models to determine commission.

Notice the time I take to break down the word problem. Modeling the deep understanding of each piece in the problem is important and it is the most difficult skill to develop and the most influential to success in common core word problems. We are practicing MP1.

After reviewing the solution to the sample problem in the notes I have students copy the definition of a tip, or gratuity, and once again caution them to make sure they know what the question in the word problem is asking them to find. Sometimes they will just want the piece, sometimes they will want a total.

20 minutes

Students receive a problem solving Task assignment. A timer is set at the board with 10 minutes. Students are instructed to show bar models for the first 4 problems in the assignment and that they may work with neighbors during the first ten minutes of this section. Students who complete the first 4 problems, with bar models and other pertinent work included, will be awarded achievement points, booth seats, and will be asked to display their work on the board.

The remaining 10 minutes of this section will be completed independently and silently.

## Closing

10 minutes

In the last 10 minutes of class I will be asking students who were able to put work up on the board to present their calculations and walk us through the logic behind their bar models. If given time, I will ask other students to share out any other strategies they found helpful on this assignment.

It is important to note the different types of questions that could be asked in a word problems and the implications those questions have on the work to be completed. When do we calculate the piece only? When do we add that calculated piece to another value to get a total? The following facts should be highlighted for each question reviewed in class:

#1 – asks for the piece only by asking for the shipping cost

#2 – asks for the amount left as the extra tip only, not the total spent. We do not add 2,000 to the tip

#3 – asks for the commission alone; simply calculate 12% of \$2,000.

#4 – the first part asks for the taxes alone; the second question asks for the grand total of staying for 10 nights. This is a great opportunity to highlight numeric expressions

It will be announced that all of the work and answers to today’s assignment will be on our class website so that students can use it to study for tomorrow’s quiz.