Video: Finding the Missing Addend in Addition Equations with Numbers up to 5

Find the missing number. 1 + _ = 4.

02:06

Video Transcript

Find the missing number. One plus what equals four.

We can see two missing spaces here. To begin with, we’re given an addition equation. And instead of the missing number being at the end like it often is, we can see that one of the numbers we’re adding is missing. One plus what equals four. And underneath this equation, we can see the same addition shown using pictures. One ball plus how many balls equals four balls. The number that’s missing in this question is one of the parts. To help us understand this, we could sketch a part–whole model. Now we know the whole amount because the answer to the addition or the total is four. This whole amount is what happens when we add two parts together.

What else do we know? Well, we also know that one of the parts is worth one. So one is a part, another number is a part, and the whole amount is four. How can we find the missing part? Well, we could count on from the part we already know. Let’s use cubes to help us do this. This cube represents the part that we already know, which is worth one. Now let’s count on until we get to four cubes, two, three, four. We’ve counted on three more cubes to make a chain of four cubes. So we can complete our part–whole model using the number three. One and three go together to make four. Four is equal to one and three. Our missing number is three.

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