Recently I was in a Grade 6 classroom and the teacher gave this problem to her students to solve.
Ms H is planning on cooking a turkey. She read online that it takes 20 minutes to cook 500 grams of turkey. The turkey weighs 9.75 kilograms. About how long will it take to cook the whole turkey?
This is a great example of a proportional reasoning problem. Students need to have knowledge of the relationships between grams/kilograms and minutes/hours.
When students work on a problem like this we want them to understand that they can figure out any size turkey based on the time/weight relationship (Big Idea).
On another note: With students I always try to remember to read 9.75 as 9 and 75 hundredths (fractional language) instead of 9 point 75. This helps with building the understanding of the relationship between fractions and decimals – a fragile concept for many!
In the first photo students are demonstrating an understanding of the relationships I mentioned. My feedback: Do you have to fill in the whole chart? At what point could you have made a calculation based on the pattern you have identified? I want them to see that at the 200 minute/5000 grams mark they could have “doubled” both. That’s multiplicative thinking!
In the second photo the students have followed a fairly straightforward procedure for solving this. I chose this particular piece to share because of the way they have annotated or labeled their numbers in the calculations. This is a strategy that I promote because it encourages students to think about what the numbers represent in the problem and it gets away from elaborate explanations that do not add value to the solution.