## Subtraction and Unknown Addends (to 20)

#### Aligned To Common Core Standard:

**Grade 1 Operations** - OA.4

What Are Unknown Addends
To understand addition equations, the use of addends is highly common. The use and function of addends can teach you 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 an additional sum, for example;

2 + 3 = 5

Here, 2 and 3 are the addends, while 5 is the sum of those addends. Addition sums can have more than two addends, single- or double-digit numbers. They can be positive, like 5, or even negative, such as -5.
What are unknown addends?
As the name implies, an unknown addend is basically a missing 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 unknown 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.
These worksheets have students fill in missing integers to complete the subtraction operations.

- Missing Addends Step-by-step Lesson-
How much gas does Mr. George need?

- Clocks, Dolls, and Candles Guided
Lesson - You are given a few pictures to make it a bit easier
for you to handle.

- 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 is picking flowers.
- Guided Lesson 2 - It was Spring time when I wrote this one.
- Step-by-step Lesson 1 - Rubber duckies in a box! What can go wrong?
- 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.

#### 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.