Online Circle 2: triangle and square numbers, a game with two dice

December 20, 2020, 9:00-9:30am. Nia (5), Bab (5), Gye (5), Dem (5)

Last time, Dil was playing with the cubes and making towers of 1, 2, 3, 4, and putting them next to each other. It reminded me of something I read and I created the first activity.

Task 1

Supplies: A few Mathlink or Unifix cubes.
What to do: 
- Invite the children to make a few "triangle numbers" as in the picture below, then count the number of cubes in each triangle. Write the numbers down (the first three are 1, 3 and 6) 
First three triangle numbers
- Invite the children to make a few "square numbers" then count the number of cubes in each. Write them down also. 
First three square numbers
- now invite the children to take the sum of the two consecutive triangle numbers. Do they see a pattern? (answer: the sums are square numbers!)
- can the children take the cubes from two triangle numbers and make a square? 

Task 2

Supplies: two dice.
What to do: 
- Say that you are going to roll the dice, add the numbers on top, then keep track of them. It is like a number race.
- Ask what numbers could come up and write 1 through 13 and the numbers suggested on a line.  
- Ask each child what number they think will come up more often. 
- Invite the children to roll the two dice and find the sum. Then record the sum by putting an X on top of the number. The first number to get 6Xs on top wins. 

How it went

Both activities went really well. The kids likes making triangle and square numbers. They noticed that adding two consecutive triangle numbers gives a square number. I showed them how to make a square with the cubes and they were quite happy with it

Adding two consecutive triangle numbers makes a square number

The dice game was a lot of fun. Being online, I couldn’t quite see everyone’s dice and there was a suspicious “14”. I laughed and added it to the board. Nobody complained or said anything, except for Bel (8) who was watching. But in the end, 6 and 7 won.

I finished with a “magic trick”. I asked the kids to roll their two dice, add the numbers on top. Then secretly, without showing me their dice, lift them and add to that the numbers on the bottom. I then exclaimed “You got 14!”. Kids were not impressed. Gye told me show got two 5s on top, which made 10 and that was the number she wanted. The trick only works if they add four numbers accurately – I thought it was funny how they were totally non-nonplussed.

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