Day 63: 20 Percent Off or 20 Dollars Off?

6th Grade Math Standards: 6.RP.3 Use ratio and rate reasoning to solve real-world and mathematical problems, e.g., by reasoning about tables of equivalent ratios, tape diagrams, double number line diagrams, or equations. a. Make tables of equivalent ratios relating quantities with whole-number measurements, find missing values in the tables, and plot the pairs of values on the coordinate plane. Use tables to compare ratios. b. Solve unit rate problems, including those involving unit pricing and constant speed. For example, if it took 7 hours to mow 4 lawns, then, at that rate, how many lawns could be mowed in 35 hours? At what rate were lawns being mowed? c. Find a percent of a quantity as a rate per 100 (e.g., 30% of a quantity means 30/100 times the quantity); solve problems involving finding the whole, given a part and the percent. d. Use ratio reasoning to convert measurement units; manipulate and transform units appropriately when multiplying or dividing quantities.

Objective: Determine if 20% off or $20 off is a better deal

Agenda:

1. Self Assessment
2. QSSQ
3. Review the Quiz
4. My Favorite No (20% of 64)
5. 20% off or $20 off from Dan Meyer 
6. Homework Practice

Assessment: I circumvented the room as students worked on the homework and the notes. There was also the self-assessment sheet that students got after the quiz. One of the sixty students could find the answer to the my favorite no question. That student used multiplication, so I worked with that student on the ten percent rule.

Glass Half-Full: This was probably the fourth time I've used Dan Meyer's Dualing Discount activity to teach how to find the percent of a number. It was probably the best that I have done because I let the students know ahead of time not to shout out ideas to enhance the likelihood that many students would be discovering that sometimes 20% was better and sometimes $20 off was better.

Regrets: This lesson does take more than one would think just looking at the agenda and especially the dueling discount problems. I did not use all of Meyer's problems, and did not need to either. My frustration was that we could not have a discussion or a a calculation surrounding at what point does the price of the item not matter regardless of the coupon. Perhaps I could speed this up by giving students four more examples (not have them do the calculation) and then give them more time to analyze what was happening.