# Subtract By Adding

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Team Digital
CCSS.MATH.CONTENT.2.NBT.B.5

## How Do You Do Addition and Subtraction Mentally?

In this video Imani is helping Mr. Squeaks train for an upcoming track meet! As Mr. Squeaks is running, he wants to know exactly how far he has run. He learns all about the think addition to subtract strategy while training. Watch this video to learn more about how to use think addition to subtract.

## What is the Think Addition Strategy?

You may know that there are many strategies to help solve addition equations, but did you know that there are many to solve subtraction equations as well? One of those is the think addition strategy, also known as subtract using addition!

You may be wondering, how does addition help subtraction? Addition and subtraction are related, meaning that we can use what we know about one to help us with the other! When using addition to solve subtraction equations;

• First: create the subtraction equation

• Then: think of an addition fact to help you subtract. You can this by looking at the subtraction equation!

• Next: take the smaller number from the subtraction equation to create the new addition equation

• Finally: count up from the smaller number to find the answer!

## Think Addition to Subtract 2nd Grade - Practice

What is the easiest way to add and subtract numbers? Take a look at the example below and use the think addition or subtract using addition strategy to solve!

Remember to create a new addition equation, and to count up to find the answer. We can create thirty plus what equals forty-six as our new addition equation.

Thirty plus sixteen equals forty-six, which means that forty-six minus thirty also equals sixteen!

## Think Addition to Subtract - Summary

Today we learned all about think addition to subtract, which is when you subtract using addition. When using addition to subtract;

• First: create the subtraction equation

• Then: Use the smaller number to create the new addition equation

• Next: Count up to solve

Looking for extra practice? After this video check out the interactive exercises and a think addition to subtract worksheet.

## Subtract By Adding exercise

Would you like to apply the knowledge you’ve learned? You can review and practice it with the tasks for the video Subtract By Adding.
• ### Order the steps for subtracting by adding.

Hints

Re-order the subtraction equation as an addition problem by solving for 10 + ? = 23? Then count up from 10 to 23.

Solve for 30 + ? = 46 by first counting up to the next 10. Then continue counting to find the difference!

Solution

Step ONE: Create a subtraction equation.

Step TWO: Remake the equation as an addition equation, starting with the smaller number.

Step THREE: Solve the addition equation by counting up to the solution.

Step FOUR: Remake the equation again as a subtraction equation with the solution.

• ### Subtract by adding.

Hints

In order to solve with addition, rephrase the subtraction equation as an addition problem.

Re-arranging a subtraction equation as an addition problem can make it easier to count up to the solution and solve the equation.

Solution

1) 10 - 2 = ?
2) 2 + ? = 10
3) 2 + 8 = 10

A good technique to solve with addition can be to count up from 2 to 10. The difference is your answer!

• ### Word problems to equations.

Hints

When making a subtraction equation, write the larger number first and subtract the smaller number next.

If Mr. Squeaks begins at the 6 marker and runs until the 12 marker this problem would be written as 12 - 6 = ? to find how far he ran.

Solution

*Mr. Squeaks started at the 23 marker and ran to the 10 marker becomes 23 - 10 = ___
*Mr. Squeaks started at the 30 marker and ran to the 18 marker becomes 30 - 18 = ___
*Mr. Squeaks started at the 5 marker and ran to the 15 marker becomes 15 - 5 = ___
*Mr. Squeaks started at the 10 marker and ran to the 50 marker becomes 50 - 10 = ___

• ### Subtraction to addition.

Hints

When remaking an equation, the larger number in the subtraction equation will be the solution in the addition equation.

In order to solve with addition, rephrase the subtraction equation as an addition problem.

Solution

When remaking an equation, the larger number in the subtraction equation will be the solution in the addition equation.

• 10 - 4 can be re-written as 4 + ___ = 10. 10 - 4 = 6 and 4 + 6 = 10.
• 18 - 6 can be re-written as 6 + ___ = 18. 18 - 6 = 12 and 6 + 12 = 18.
• 10 - 6 can be re-written as 6 + ___ = 10. 10 - 6 = 4 and 6 + 4 = 10.
• 5 - 5 can be re-written as 5 + ___ = 5. 5 - 5 = 0 and 5 + 0 =5.
• 20 - 5 can be re-written as 5 + ___ = 20. 20 - 5 = 15 and 5 + 15 = 20.

• ### Tools for adding when subtracting.

Hints

A hundreds chart can be a good way to see the numbers while you are counting.

A number line allows you to count and add quickly with tens before you start adding ones.

A place value chart will let you easily see how many tens and ones you still need to add to the total.

Solution
• A number line allows you to count and add quickly with tens before you start adding ones.
• A hundreds chart can be a good way to see the numbers while you are counting.
• A place value chart will let you easily see how many tens and ones you still need to add to the total.
• ### Solving subtraction equations by adding.

Hints

In order to solve with addition, rephrase the subtraction equation as an addition problem.

Re-arranging a subtraction equation as an addition problem can make it easier to count up to the solution and solve the equation. Remember to rewrite again as a subtraction equation as the last step.

Solution

When remaking an equation, the larger number in the subtraction equation will be the solution in the addition equation. Then fill in the rest of the numbers step by step.

Problem 1
1) 10 - 6 = ?
2) 6 + ___ = 10
3) 6 + 4 = 10
4) 10 - 6 = 4

Problem 2
1) 16 - 14 = ?
2) 14 + ___ = 16
3) 14 + 2 = 16
4) 16 - 14 = 2