## Missing Addends

#### Aligned To Common Core Standard:

**Grade 1 Operations** - OA.4

When ever you are trying to find a sum the two values that you are adding together are each known as addends. In many cases you will have a total (sum) and need to determine one of the addends that created that sum. This is fundamental algebra. For example, if I said that there 30 tennis balls in my garage that Aunt Sue and Billy gave me. I know that Aunt Sue gave me 18 tennis balls. If we wanted to know how many tennis balls Billy gave me, this would be solving for a missing addend. Writing this is simple equation form: 18 + Billy's contribution = 30. We could solve this by simply subtracting 18 from the sum (30). This would tell us that Billy gave me 12 tennis balls. These are the types of problems that you will find in this section of our site. The worksheets are really helpful for gaining a solid command of these types of problems. They will help you frame your understanding of basic algebra and lead you in that direction. These worksheets have students find in missing integers to complete the subtraction operations.

- Missing Addends Step-by-step Lesson-
We work on this: Mr. George has 5 gallons of fuel in his car. His fuel tank has a capacity of 11
gallons. How many gallons are needed to fill the fuel tank?

- Clocks, Dolls, and Candles Guided Lesson - You are given a few pictures to make it a bit easier for you to handle and understand as you solve the problems.
- Numeric Guided Lesson Explanation - The pictures are mirrored by the numbers that they represent to make it transition with ease.
- Blank Box Problems - We give you a series of problems that have picture mirrored missing addends.
- Match the Missing Pieces - Find the missing piece of each equation. A really good way to sum it all up.

#### Guided Lessons

The pictures should help students along with these.

- Guided Lesson 1 - Nicky has to pick 15 flowers. He has picked 10. How many more flowers does he have to pick?
- Guided Lesson 2 - It was Spring time when I wrote this one. There are 9 butterflies in your yard. How many more butterflies do you need to have 15 butterflies altogether?
- Step-by-step Lesson 1 - Rubber duckies in a box! What can go wrong? Charlie has 15 kg of rubber duckies in his box. His box has a capacity of 23 kg. How many kg of rubber duckies are needed to fill the box?
- Step-by-step Lesson 2 - Sorry that I didn't give this one more personality.
- Step-by-step Lesson 3 - A quick break into word problems. Mark has 11 tons of goods in his truck. His truck has a capacity of 25 tons. How many more tons of goods are needed to fill the truck?

#### Practice Worksheets

The sheets below should start to stimulate thinking at the next level for students.

- Addition Equations - See if you can get this one to add up for you.
- Independent Practice - The diagrams used here are great to work into fractions in the next level of the core curriculum.
- Independent Practice 2- The dark part is what is missing and students need to fill in.
- Matching Worksheet - This is great to see the level that kids are thinking about. I like to just set them loose on these.

### What Are Missing Addends?

To understand addition equations, understanding the function of addends is critical. At their core addends are simply the things we add together to make a sum. Once we master this concept we begin to under the basics of number operations and the addition of sums. It will also help you enhance mathematical reasoning and problem-solving skills.
Addends are any numbers used in forming a sum, for example;

2 + 3 = 5

Here, 2 and 3 are the addends, while 5 is the sum of those addends.

The formation of a sum can have more than two addends, in fact there can be almost an infinite number of addends. Addends can come in all different sizes. In this section we are just focusing on using single- or double-digit numbers. They can be positive, like 5, or even negative, such as -5.
As the name implies, a missing addend is basically a lost or unknown digit in an additional sum. In a mathematical equation like this one;

4 + _ = 8

This equation contains two addends; one of them is known, and the other one is unknown or a missing addend. This sum is called a problem of unknown addends.
The basic purpose of learning missing addends is to familiarize yourself with the basics of algebraic math and develop an understanding beyond just adding given digits. This means if you see a problem like; 5 + 6 = 11 and then you get to solve one like; 5 + _ = 12, you can use your basic understanding of addends to solve the problem.

### An Example Missing Addend Problem

**Problem** - Jessica loves playing tennis. She practices almost every chance that she gets. She brought 21 tennis balls with her to practice. She found 14 of them on one side of the court. All the other balls were on the other side of the court. How many tennis balls were on the other side of the court?

**Solution** - Start by identifying what we are being asked. We are looking for a portion of the total (21) number of tennis balls that we started with. We know that 14 of the 21 are already account for and we are looking for what is left. We can put this in the form of an equation like this:

14 + missing tennis balls = 21.

To find the missing addend, we would rearrange this equation like this:

missing tennis balls = 21 - 14.

missing tennis balls = 7.