Video: Writing the Missing Symbol in Addition and Subtraction Equations

Fill in the blank to find the missing symbol: 12 _ 2 = 14.

02:29

Video Transcript

Fill in the blank to find the missing symbol. 12 what two equals 14?

This statement is missing a symbol. We know that the symbol can’t be one that compares the numbers because it wouldn’t make sense. 12 equals two equals 14. Even 12 is greater than two, which would make sense, isn’t correct because we’ve got an equal sign and then 14 on the end. 12 is greater than two, but two is not equal to 14. And so we know the missing symbol must be one of the four operations: add, subtract, multiply, or divide.

Let’s go through each symbol to find the answer. We know 12 is made up of one 10 and two ones. What if our symbol was the plus symbol? Then we’d need to add two to 12. So let’s add two ones and see what happens to 12. One, two. 12 plus two does equal 14. 14 is two more than 12. So we’ve found the missing symbol.

Let’s just quickly go through the other three symbols to prove that we’re correct. 12 take away two leaves us with just one 10 on its own. Taking away makes a number get smaller, so we know it could never be a subtraction symbol. Let’s use number blocks for the next one. 12 multiplied by two is the same as 12 doubled. Now this will make the total get larger. But we can see that it’s going to be a lot larger. 12 doubled equals 24.

And finally, we know it’s not going to be our last symbol, which is divide, because this is going to make 12 smaller. 12 split into two equal groups or halved gives us an answer of six. So although we knew that this was an addition sentence quite early on, we’ve now proved why none of the other symbols make sense. 12 plus two equals 14. The missing symbol is plus.

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