How to Complete the Addition Sentence

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  • 0:05 Addition Sentences
  • 0:33 Missing Terms
  • 2:14 Examples
  • 3:13 Lesson Summary
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Lesson Transcript
Instructor: Yuanxin (Amy) Yang Alcocer

Amy has a master's degree in secondary education and has taught math at a public charter high school.

In this video lesson, you will learn how to complete an addition sentence when you have one missing term. See what an addition sentence looks like and the possible missing terms you can expect to find.

Addition Sentences

In math, addition sentences are very popular. An addition sentence is a mathematical expression that shows two or more values added together and their sum. So, the mathematical expression 1 + 1 = 2 is an addition sentence.

You'll see these types of problems often in your math classes, and you'll use these types of problems often in daily life. For example, when you go shopping, you might have to add two prices together. When you do this, you are actually completing an addition sentence and solving it!

Missing Terms

In both real life and math class, you might have to find missing terms in addition sentences. Each number is considered a term in an addition sentence. So, in the addition sentence 1 + 2 = 3, each of the numbers (1, 2, and 3) is a term.

For example, in math class, you might be asked to find the missing term in the addition sentence 2 + ? = 5. In real life, you might have an addition sentence such as 4 + 9 = ?. The missing term can be located anywhere. It could be the first term, the second term, the last term, or any term in between.

Finding The Missing Term

Figuring out what the missing term equals is a bit different depending on the location of the missing term. If the missing term is located on the side with the addition operator, you will need to perform some subtraction to find your missing term.

For example, to solve the addition sentence 2 + ? = 5, you need to subtract the 2 from the 5 to find out what the missing term equals. Why do you need to do that? Because you are trying to find out what number added to 2 will give you 5. The answer, then, is 5 - 2 = 3. The rule here is: if the missing term is on the side with the addition operator, you subtract the number that is already on that side from the sum, or the number on the other side.

If the missing term is by itself on the side without the addition operator, you simply add up your numbers to find the missing term. For example, to solve the addition sentence 4 + 9 = ?, you would add up the 4 and the 9 to find your answer. Your answer here, then, is 4 + 9 = 13.


Let's look at a few example problems.

? + 11 = 20

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