Video: Finding All Ways to Subtract from 5

Find the missing equation.

02:18

Video Transcript

Find the missing equation. Five take away one equals four. Five take away two equals three. What? Five take away four equals one.

In this problem, we’re shown four pictures of ten frames, and they each show a subtraction. If we look at each ten frame, we can see that the top row of each one is completely full. In other words, we’re starting with five counters every time. That’s why when we look at the number sentences or equations that follow these pictures, we can see the number five is first. It’s the number we’re starting with. But can you see we don’t have a subtraction for our third picture. It’s missing. And the question asks us to find this missing equation.

Well, we know which number to start with. Just like all the other pictures, we have five green counters to begin with. If we look at our first picture, we can see that we’re taking away a small amount of counters, one. Then in the second picture, we’re taking away one more than this. We take away two. By taking away one more each time, we know that we can find all the different possibilities. So if we take away two in this one, in the next calculation, we need to take away three.

Let’s check the diagram to see if this makes sense. Yes, we can see that we’re taking away three out of our five counters. All we have to do now is to think about what the answer is going to be. What number goes with three to make five? We could imagine a cube train containing five cubes. And if we break it apart so that there are three in one group, we know that there’ll be two in the other group. Five counters take away three counters leaves us with two counters. And we can see in our last equation we take one more again. Five take away four this time equals one. We know that three and two go together to make five. And so our missing equation is five take away three equals two.

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