We have students find a missing addend to a sum in these worksheets.

This is the origin of where algebra begins for students. We start with larger numbers than we would expect, but this concept starts to pop out at us now. These worksheets will begin to help student envision these problems as equation. Each of the problems is presented in horizontal view and is complete with an addition equation that is missing numbers. The missing values can present as a full addend, sum, or portion of either one. A good way to approach the Do Now section is to have students write an explanation for how they approach the problem itself. Missing algebraic sums was considered to be one of the most challenging topics for lower middle school students. That is according to National PETS tests. Who knows if the problems were not clearly written?

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Print Missing Number Addition Worksheets

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Missing Number Addition Skill Lesson

Missing Number Addition Skill Lesson

Students will walk through a missing addition problem that presents as this: A number that when added to 158, gives a sum of 489. We walk you through finding the number.

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Missed Addend Practice Worksheet

Missed Addend Practice

You will look for a value that satisfies this addition problem: A number that when added to 245, gives a sum of 385. You get a fully completed example and two problems to work on.

Practice the Skill Worksheet

Practice the Skill

We keep the sums rather large on this worksheet. Might require a little more time than you first anticipated.

Partial Sums and Addends Worksheet

Partial Sums and Addends Worksheet

The sums here are more toward the mid-line of the 500 level. There may be a whole or portion missing from each of these.

Missing Parts Worksheet

Missing Parts Worksheet

Give yourself eight reps to work through quickly. You will quickly diagnose what addend or part of it is missing to make these sums.

Warmup Worksheet


Get the class started with three problem that you can all work on together. There are 3 problems that you will need to find the values of the missing symbols for.

Missing Number Addition Lesson

Missing Number Addition Lesson

This will walk you through an entire problem and then you will complete 2 practice problems on your own. Missing number has to be found, which when added to 260, gives a sum of 698.

Practice Worksheet 1

Practice Worksheet 1

We removed the boxes to allow for more whitespace to work around with.

Worksheet 2

Worksheet 2

Yes, all of these problems have sums that add up greater than 1,000. This adds an element of difficulty.

Review Worksheet


This makes for an awesome homework sheet. Give it a try!

Missing Digit Addition Quiz

Missing Digit Addition Quiz

Tests your skills out against the gear here. Test your skills.

Do Now Worksheet

Do Now

This is can either be used to introduce the topic, review the topic, or simple used as a quick challenge reminder.

How to Solve Missing Digit Addition Problems

Most addition problems involve two numbers that are relatively easy to add together. However, there are times when one or more of the digits in one of the numbers is missing, which can make the problem a bit more challenging. However, by using some simple mental math strategies, you can still arrive at the correct answer.

A standard double digit addition problem consist of two addends (2-digits each) that when added together create a sum. If you subtract either addend from the sum, you will be left will a value equal to that sum. This can allow you to rearrange things all over the equation.

Examples of How to Solve These Types of Problems

When One-Digit Is Missing

Adding 8+9 is pretty simple. Most people would just put the 8 in the one's column and carry the 1 over to the tens column, giving us a sum of 17. However, what if one of the digits is missing? For example, what if we were given the problem 8+__=17? In this case, we would still carry the 1 over to the tens column, but we would have to figure out what number goes in the blank space.

To do this, we can use a technique called estimation. We get 17. Now let's see what happens when we add 8 + 10. We get 18. Now, notice that when we add 8+9, the one digit is 7; when we add 8 + 10, the ones digit is 8. So, we can estimate that the absent integer in our problem is probably a 9.

Besides estimation, there is another method that we can use to solve these types of problems. Let's consider the same example, 8+ __ = 17. Now, we need to subtract 8 from 17, and we will get the missing digit, which is 9. This method is sometimes difficult when subtraction involves numbers having more than two digits.

When Two Digits Are Missing

Let's try an example where more than one digit is absent. For this example, let's say we're given the problem __+__=15. To solve this problem, we can again use estimation.

First, let's add 8 + 8. We get 16. Now let's add 7 + 7. We get 17. Notice that when we add 8 + 8, the ones digit is 6; when we add 7 + 7, the ones digit is 4. So, we can estimate that the missing digits in our problem are probably 8 and 7, which would give us a sum of 15. However, there can be multiple combinations when we have problems with both digits missing.

These Problems Improve Your Kid's Cognitive Development

Most parents think teaching their kids how to make additions with missing digits is a waste of time. They feel that their kids can easily do these kinds of problems mentally, and there is no need to write them down. However, in actual missing digit addition problems can help your kid develop a better understanding of addition concepts.

Develop Critical Thinking

When you ask your kid to solve a missing digit addition problem, they use various addition strategies. For instance, they might use the commutative property of addition (i.e., the order of the addends does not matter) to simplify the problem. Alternatively, they might use the associative property of addition (i.e., the grouping of the addends does not matter) to simplify the problem.

Using these strategies, your kid can break down the addition problem into smaller, more manageable pieces. As a result, they can better understand the concept of addition and solve problems more efficiently.

Develop Problem-Solving Skills

In addition, missing digit addition problems can also help your kid develop their problem-solving skills. When solving a missing digit addition problem, your kid must think critically and use their reasoning skills to determine the value of the missing digit. This problem-solving is an essential skill that will help your kid in all areas of their life, not just in mathematics.

Wrapping Up

So, the next time you look for a way to help your kid develop a better understanding of addition, try teaching them how to solve missing digit addition problems. Missing digit addition problems can be challenging, but using estimation can help you solve them.

Just look at the numbers around the missing digits and see which ones make the most sense. With a bit of practice, you'll be able to solve these problems in no time!