Balloon subtraction

We have been learning about subtraction in Te Awa. We started off with a subtraction problem.

Popping balloons

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Core

Annotation

Sam understands that this is a subtraction problem. He carefully checks by one-to-one counting each finger as he subtracts the correct amount and he checks that he has answered the question, “how many left?”

Problem: Popping balloons 

The teacher shows this problem to the student and reads it with him as required:

There were 10 red balloons. 4 went pop! How many balloons were left?

Student response

Sam holds up 10 fingers. He carefully folds down 4 fingers, counting aloud as he does so. He checks again that 4 have been taken away. He keeps 2 hands (6 fingers) in the air and counts each of his 6 remaining fingers moving each as he does, to indicate to himself that they have been counted. He says, “There’s 6 left. I took away the 4 and counted.”

Teacher:	Tell me what you know that helped you.
Sam:	I know I have to take some away because they popped.
Teacher:	How would you write that?
Sam:	I’d write 10 because that’s how many there were at the start. (He draws 10 balloons.) I do a takeaway sign and four because that’s how many popped (He deletes 4 balloons with lines to show they have popped) and then I write equals six because that’s what’s left.

Then Miss Simmonds gave us a problem with 20 real balloons.

We had a lot of fun working out the answer when Miss Simmonds popped some balloons.

20 - 7 = ____

Then we got to play with our balloons on the field.

Lining up 20 balloons on the field was a bit tricky.

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