[playful music] - Hi, everyone.

Welcome to my classroom.

I'm Miss Zoe.

I have here with me today?

- Malena.

- Malena.

And she's gonna help me work on what we call inverse operations.

And inverse operations is when you take a set of two opposite operations, like addition and subtraction, and you show how they are related.

And I'm going to give you an example, so, [paper crackling] [bright music] if I were to say 10 minus 2 equals 8, Malena would write it as addition.

- 2 plus 8 equals 10, - 2 plus 8 equals 10.

So we're gonna work on that with our counters as well.

[bright music] [eraser scratching] Now would we be able to do 8 plus 2 equals 10?

- Yes.

- Could we do 10, let's say, plus 2 - Equals 12.

- Equals 12, right?

So they're both addition, so that rule doesn't work, right?

Our inverse rule.

What if I did 7 plus 4 equals?

- Well, that equals 11.

- Okay, so- - Because 7 plus 3 equals 10 and 10, but 3 plus 1 equals 5.

Wait, 3 plus 4, no, 3 plus 1 equals 4.

And 4 plus 7 is, 4 one more than 3, so it would be 7 plus 4 equals 11.

- Okay, so let's count one, two, three, four, five, six, seven, eight, nine, 10, 11, so 7 plus 4 equals... [bright music] [chips clicking] Two, four, six, 8, 10, 11.

[bright music] So what would the inverse operation be?

- 11 minus 7 equals 4.

- 11 minus 7 equals 4.

So let's look at the chips.

I'm going to take this group.

This group, I'm gonna move my 11 chips here.

[chips rattling] [mischievous music] [paper crackling] And then Malena said?

- 11 minus 7 equals 4.

- So I'm gonna put seven here, two, four, six, seven.

And I'm left.

- Four.

- With four.

All right, friends, so let's just recap what we just did with Malena.

So remember the inverse operations are the two sets of opposite operations, like addition and subtraction, like we just did.

And when you do that, you have to, if you have an addition problem, and a subtraction problem, you have to start with the largest number for the subtraction.

So let's just review that.

[pen pops] [bright music] If I have 6 plus 4 equals 10, [paper crackling] [bright music] 6 plus 4 equals 10, [board rattles] and I am going to make that into a subtraction problem, I can't take 10 away from 6, 10 is a bigger number, so I have to start with 10 minus 6 equals 4.

[chips rattles] If I have 6, one, two, three, four, five, six, plus 4, 1 two, three, four, let's count them all together.

One, two, three, four, five, six, 7, 8, 9, 10.

So I would put [chips rattling] 10, 1, 2, three, four, five, six, seven, eight, 9, 10, 6 plus 4 equals 10.

Now what you'll see is we're not gonna change the number of counters in each square.

We're just going to move them around.

And like I said, you have to take the biggest quantity, which is 10 to subtract from.

So 10 minus [chips rattling] [bright music] 6 equals 4.

[chips rattling] [bright music] So I haven't added any counters, I haven't taken away any counters.

I've only used a group that we started with.

All right, well, I hope you had fun today.