Reflection: Student Led Inquiry Multiplying with Mathmaster Chef (Day 2 of 2) - Section 2: Warm up


In the warm up I neglected to clarify that I was looking for "equal" bunches of hot and cold cubes and my students were coming up with many different ways to lower the temperature 30 degrees that would not lead to multiplication in addition to a few that would. Because they were so actively engaged in figuring out their own way I decided to let it go and let them explore. In the end, my students not only made the multiplication connection, but also concluded that it was the most efficient way! Rather than prove too vague, the question opened up more room for students to ask questions and make conclusions.

Some of the initial suggestions were:

  • Add one bunch of 5 cold cubes, one of 10 cold cubes, one of 7 cold cubes, and one of 8 cold cubes (-5 + -10 + -7 + -8)
  • Add one bunch of 20 cold cubes and one bunch of 10 cold cubes (-20 + -10)
  • Add one bunch of 15 cold cubes and remove one bunch of 15 hot cubes (-15 - 15)
  • Add two bunches of 15 cold cubes (2 x -15)
  • Remove two bunches of 15 hot cubes (-2 x 15)
  • Add three bunches of 10 cold cubes (-10 + -10 + -10 or 3 x -10)

One of the questions I overheard from a math family group was "wouldn't it be easier if the bunches were all the same size?" This was a game changer that got this lesson back on my intended track. But it was so much more powerful since it came from a student!

I addressed this question to the class by saying:

"Taylor has a question that we might want to think about. She has asked if it would be easier if the bunches were all the same size. Taylor, can you tell us a little bit about what makes you wonder that?"

Taylor surprised me again by referring back to the context and pointing out that in a restaurant kitchen you need to move fast and you don't want to look for the right size bunches. She also pointed out that if the bunches were already in the pot, you might not be able to see into the pot and you might not get the right sized bunches if they were all different.

I asked the groups to discuss how equal sized groups might make the job easier and how we might go about solving the problem differently. Then I got the solutions I had hoped for:


  • Add 2 bunches of 15 cold cubes
  • Remove 2 bunches of 15 hot cubes
  • Add 15 bunches of 2 cold cubes
  • Remove 15 bunches of 2 hot cubes
  • Add 3 bunches of 10 cold cubes, etc.


After reflecting on this lesson I decided to try and ask questions in a more open ended way that might generate student questions and even raise the 'big idea' questions!

  My mistake improved this lesson
  Student Led Inquiry: My mistake improved this lesson
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Multiplying with Mathmaster Chef (Day 2 of 2)

Unit 4: Operations with Integers
Lesson 21 of 24

Objective: SWBAT multiply integers using the rules illustrated by the context of hot and cold cubes.

Big Idea: Students will be able to discover the rules for multiplying integers.

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6 teachers like this lesson
Math, Number Sense and Operations, Operations and Expressions, integer multiplication, multiplying negative numbers, student led inquiry
  35 minutes
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