About this video
The video adds 2 green balls and 3 purple balls to get 5, then takes balls away from 5. Five minus two is three and five minus three is two. This shows that addition and subtraction are linked: if two numbers add to a total, taking one away from the total leaves the other.
You'll be able to
- add two groups to find how many altogether.
- subtract by taking away from a group.
- use an addition fact to find a related subtraction fact.
Key words
- altogether
- All the things put together; it tells you to add.
- subtract
- To take some away and see how many are left.
- take away
- Another way to say subtract.
Transcript
I have two green balls and three purple balls so how many balls do I have altogether? So two green balls and three purple balls is going to be 5 balls altogether. We can count them; one, two, three, four, five. Now what if we did something a little different? Let's start with the five balls, and let's take away two.
Let's subtract two of these balls. Take away one and two, and what are we left with? We are left with one, two, three balls. We're left with three balls. You might see a pattern here; two plus three is equal to five but if you start with five and take away two, you're going to be left with three.
Look how they're arranged. Two plus three is equal to five and five minus two is three. It works the other way around. If I start with five and I were to take away three, if I subtract one, two, three, what am I left with? I'm left with one, two, I'm left with two.
So two plus three is five, three plus two is five, which is another way of saying that five minus two is three, or five minus three is two. Take a look at this, it's a really important idea to understand in math. If you add two numbers and you get another number, then you take the result and subtract one of these you're going to get the other number.
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