Bài 12: The minus sign and subtracing

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 https://www.youtube.com/watch?v=YyafUPs005s

Introducing the minus sign and subtraction.

Starry, are these magnets? Oh, they are. Look the number 1-2-3-4-5-6-7-8 and 9.

And this is a plus sign. We use this to do addition.

Now, Do you know what the sign is Starry?

You don’t. This is the minus sign.

We use this when we do subtraction.

Remember take away.

Wait, let me explain!

Suppose I have 5 marbles and I gave away 3 marbles.

How many marbles would I have with me?

First I write the number 5, then I write the number 3 below it.

Then I put the minus sign to show subtraction that 5 minus 3 reaches 2.

Now here are 7 triangles, I take away 4 triangles.

How many triangles do I have left?

I first write the number 7, next I write the number 4 below it, then put the minus sign.

Now 7 take away 4 is 3.

And here are 8 bows. I take away 2 bows. How many bows do I have left with me?

Write the number 8, next write 2 below, then the minus sign. Now subtract 8 minus 2 is 6.

Finally, here are 9 cubes, I take away 5 cubes. How many cubes do I have left?

We first write the number 9, next write the number 5 below, now the minus sign, next we subtract 5 from 9, so 9 minus 5 is 4.

Starry, let do an activity together!

Look at the picture and subtract.

Dash marbles minus dash marbles equals dash.

8 marbles minus 2 marbles equals 6 marbles.

Dash marbles minus dash marbles equals dash.

5 marbles minus 1 marbles equals 4 marbles.

Dash marbles minus dash marbles equals dash.

4 marbles minus 4 marbles equals 0 marbles.

Dash marbles minus dash marbles equals dash.

7 marbles minus 5 marble equals 2 marbles.

Dash marbles minus dash marbles equals dash.

10 marbles minus 8 marble equals 2 marbles.

Dash marbles minus dash marbles equals dash.

4 marbles minus 3 marbles equals 1 marbles.

In this activity we have to choose the correct answer from the bracket.

6 minus 1 equals dash, 4 or 5. 6 minus 1 equals 5.

7 minus 6 equals dash, 1 or 3. 7 minus 6 equals 1.

5 minus 5 equals dash, 1 or 0, 5 minus 5 equals 0.

8 minus 5 equals dash, 3 or 5, 8 minus 5 equals 3.

6 minus 3 equals dash, 0 or 3, 6 minus 3 equals 3.

9 minus 4 equals dash, 5 or 4, 9 minus 4 equals 5.

Remember Starry, when you see the minus sign (-) do subtraction.

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