About this video
This video shows that subtracting means taking things away. It works out 4 minus 3 by drawing 4 objects and taking 3 away, then 5 minus 2 by drawing 5 things and taking 2 away. It also shows that 3 = 5 - 2 and 5 - 2 = 3 mean the same thing.
You'll be able to
- explain that subtracting means taking some away.
- draw objects and take some away to find a difference.
- read 3 = 5 - 2 and 5 - 2 = 3 as the same fact.
Key words
- subtract
- To take some away from a group to see how many are left.
- minus
- The word we say for the - sign, which means take away.
- left over
- The things you still have after you take some away.
Transcript
Voiceover:Let's explore what it means to subtract numbers. So let's say that I want to figure out what 4, what 4 minus 3 is. 4 minus 3. So one way to think about this, is you start with 4 objects. And so let me just draw 4 objects. So there I have 1, 2, 3, and 4.
And when I ... So this is the 4 objects right over here. And when I say minus 3, or if I'm going to subtract 3 from the 4, one way to think about it is, I'm going to take 3 of these 4 objects away. So let's do that. So I'm going to take away 1, I'm going to take away 2, and I'm going to take away 3.
Notice, I took away 1, 2, 3 objects. So how many do I have leftover? Well, if I start with 4 and I take away 3, I subtract 3, 4 minus 3, I am left with, I am left with, 1 object, right over here. So 4 minus 3 is equal to, is equal to 1. Fascinating. Let's do another one of these.
Let's figure out what 5, what 5, what 5 minus 2 is. And let's write it this way. Let's say we want to figure out something, some question mark, some question mark ... Actually, let me just clear this out. I'll just do it right over here, actually. So let's say we have some question mark.
So there's some unknown number right over here. So I'll just put a question mark over here. And we say that unknown number is equal to, is equal to 5, 5 minus 2. Minus 2. Minus 2. So what is this going to be? Well let's visualize it. This means I have 5 things and I'm going to take away 2 of them and this is going to be what I have leftover after I start with 5 and take away 2.
So I have 1, 2, 3, 4, 5 things. Now I am going to take away 2 of them. So I'm going to take away 1 and 2. So I took away 1, 2 objects. So how many do I have leftover? Well, I have leftover these, these ... Let me do this in a different color. I have leftover these purple things right over here.
So how many is that? How many do I have leftover? Well, I have leftover 1, 2, 3 of my original 5. So something is equal is 5 minus 2. That something is 3. 3 is equal to 5 minus 2. Let me just replace this with a 3. So we see that 3 ... Actually, let me do the 3 in the same color as this green.
So we see that 3, 3 is equal to 5 minus 2 or we could say that 5 minus 2 is equal to 3. Either way.
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