Balance Addition and Subtraction Equations up to 100

β
You've just balanced **addition and subtraction equations** with numbers up to 20.

Now, let's try balancing equations with bigger numbers! π€

But first, let's review the **Whole-Part model.** It helps us balance equations.

Look at this equation. π

**17 + 5 = 22**

What does this equation tell us? π€

β It tells us about the parts that make a whole.

22 is the **whole **and 17 and 5 are its **parts.**

For any **Whole-Part model:**

**Adding **the parts gives the whole.

Part+Part=Whole(ADDITION)

**17**** + ****5**** = ****22**

**Subtracting **one part from the whole gives the other part.

Whole-Part=Part(SUBTRACTION)

**22**** - ****17**** = ****5**

β
We can use the whole-parts model **to find missing numbers **in equations.

π Let's look at an example.

**23 + ****?**** = 58**

π€ How will you find the missing number here?

We can use the whole-parts model! π€

This is an **addition **equation.

Can you tell which number is the **whole **here? And which numbers are the **parts?**

**23 + ****?**** = 58**

Very good! π

β
58 is the **whole,** and 23 and the missing number are the **parts.**

Can you think of a way to find the missing part? π€

Very good! π€

β
We can **subtract 23 from 58 **to find the missing part.

**58 - 23 = ****35**

The missing number is **35!**

23 +35= 58

__

π Let's try this equation.

**?**** - 49 = 15**

This is a **subtraction **equation.

Can you tell which number is the whole and which numbers are the parts? π€

**?**** - 49 = 15**

Correct! π

β
Here, the missing number is the **whole **and 49 and 15 are the **parts.**

How can you find the missing number? π€

You got it! π€

β
We can **add 49 and 15 **to find the missing number.

**49 + 15 = ****64**

The missing number is **64!**

64- 49 = 15

Nice work! π

π Sometimes, we might have an equation like this.

**?**** + 9 = 77 - 51**

Can you tell what the **equals (=) sign **in this equation means? π€

That's right! π

The **equals sign (=) **means that both sides of the equation have the **same value.**

π€ How can you find the missing number in this equation?

It's simple! π

π First, **simplify **the side that is complete.

Let's try it!

**77 - 51 = 26**

Great job! π This is the **answer to both sides.** It's called the common answer.

β
Now, let's **use this common answer **to find the missing number.

**?**** + 9 = 26**

This is an **addition **equation.

Can you draw a **whole-parts model **for this equation? π€

**?**** + 9 = 26**

Nicely done! π

Now, how can you find the missing number? π€

Very good! πWe subtract the part we know from the whole.

**26**** ****- 9**** ****= ****17****(****Whole ****- ****Part ****= ****Part****)**

The missing number is **17.**

**17**** + 9 = 26**

Let's put 17 in our original equation!

17+ 9 = 77 - 51

π Let's try another example.

**44 + 16 = 85 - ****?**

Do you remember the first step? π€

β
First, we** simplify **the complete side to find the common answer.

**44 + 16 = 60**

β
Now, we **use this common answer **to find the missing number.

**60 = 85 - ****?**

For this we draw a **whole-parts model.**

(**Remember**!** ** This is a **subtraction **equation.)

**85 - ****?**** = 60**

β Now, we use this model to find the missing number.

**85 - 60 = ****25**

The missing number is **25.**

44 + 16 = 85 -25_

π Let's try one last example.

**?**** - 29 = 27 + 18**

You know how to do this! Go ahead! π

β
First, we **find the common answer **using the complete side.

**27 + 18 = 45**

β
Now, we **use the common answer **to find the missing number.

**?**** - 29 = 45**

This is a **subtraction **equation.

The **whole-parts model **for this equation looks like this:

**?**** - 29 = 45**

β To find the missing number (the whole), we can add the parts.

**29 + 45 = ****74**

The missing number is **74.**

74- 29 = 27 + 18_

You did a great job! π Now, you can move on to the practice.

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