How would you solve this question:
Reader Question #1.
To make 10 pancakes, a recipe calls for 16 Tbsp of sugar.
How much sugar is used for 17 pancakes?
Take your time. Write down the solution that comes to your mind. Go ahead...
Good. Got it? Save your solution until end.
Here's the lesson I did with students and some observations.
This is the pre-activity from MARS, thanks to Fawn Ngyuen for citing this resource.
- Often students found the price of one pancake (Unit Price) and then x 10.
- Less frequently students did 10 ÷ 4 (Scale Factor) then x 6.
- Doubling and halving was quite popular.
- One student did cross multiplication "because that's the way I learned it."
- the increase in size was easier than the decrease.
- doubling and halving was used for some of the .75 and the 2.5
- No cross multiplication was used.
- some adding of 15 to get 31 was used.2
- this question, more so than any other, was left blank.
- Scale Factor
- Unit Price
- Doubling and Halving
- And the rarely used Cross Multiplication
- 15 min. working on the sheet individually. (took me 35)
- 15 min. producing small group solutions (took me 40+)
- 20 min. Class discussion (took 40)
- How much for five cans?
- How much is one can?
- What happened to the missing can?
- Where are they shopping?
1. [I have to say the word 'Proportional' in combination with 'Reasoning' is a tough sell for students. We need a snazzier name. Rates and Ratios is only slightly better. Is Scale enough?]↩ 2. [I should submit that for a math mistake]↩