How to Balance Addition and Subtraction Equations up to 20

Look at these two equations. 👇

14 - 3 = 11

6 + 5 = 11

What do they have in common? 🤔

Very good! 😃 They both equal 11.

      When two expressions (addition or subtraction) have the same value, we can write them on either side of an equal sign.

Each expression will be half of a larger equation:

The equals sign (=) tells us that both sides of the equation have the same value. ✅

      When both sides of the equal sign have the same value, we say the equation is balanced!

Is the following equation balanced?

13 + 4 = 20 - 3

👉 To see, let's simplify both sides of the equation separately.

13 + 4 = 17

and

20 - 3 = 17

Both sides of the equation have a value of 17.

So yes, the equation is balanced!__

Balancing Addition and Subtraction Equations

What about this equation: 

16 - 7 = ? + 1

How do we find the missing number that will keep it balanced? 🤔

      To find the missing number in an equation, first simplify the side that is complete. It's the side without any missing numbers.

Let's try it out! 🤗

16 - 7 = ?

😎 Let's simplify this subtraction operation down to a value.

16 - 7 = 9

Good job!

Now, we can write an easier equation to solve:

9 = ? + 1

Think about the whole-part model in your head to find the missing number. 🤗

What is missing, the part or the whole?

👍 This addition equation tells us that 9 has been split into 2 parts. One part is missing!

The missing part is 8.

8 + 1 = 9

Let's put 8 in our original equation:

16 - 7 = 8 + 1

Great job! You balanced the equation. 🎉

👉 Let's try another example.

Example 1

? - 4 = 3 + 3

How will you start? 🤔

✅ First, simplify the complete side.

3 + 3 = 6

Now, rewrite the simplified equation.

? - 4 = 6

What's the next step? 🤔 

That's right, we think about the whole-part model.

This subtraction equation tells us that 4 has been taken away from a bigger number to get 6.

So we're missing the whole. We add the two parts, 4 and 6.

The missing number is 10.

10 - 4 = 6

Let's put it back in our original equation: 

10 - 4 = 3 + 3

Let's try one last example!

Example 2

13 + 2 = 19 - ?

First, simplify the side you can!

13 + 2 = 15

Now, use this answer to find the missing number.

15 = 19 - ?

      This subtraction equation tells us that a part of 19 has been taken away to get 15.

What is the missing number? 🤓

You got it! 🤗 The missing number is 4.

19 - 4 = 15

Let's put 4 in our original equation:

13 + 2 = 19 - 4

Great job! 🎉 You balanced the equation.

Now, ace the practice. 😃