# Adding and Subtracting Mixed Numbers

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CCSS.MATH.CONTENT.4.NF.B.3.C CCSS.MATH.CONTENT.4.NF.B.3.D

## Mixed Numbers – Adding and Subtracting

Have you ever tried making slime at home? It is a lot of fun!
For the special slime we want to make today, the recipe is difficult to read, as it contains mixed numbers. In order to figure out how much to use of each ingredient, we need to learn and practice adding and subtracting mixed numbers. Not to worry – the following text teaches us everything we need to know.

### Steps to Adding and Subtracting Mixed Numbers

A mixed number is a combination of a whole number and a fraction. When you practice adding and subtracting mixed numbers with like denominators, you can follow these three steps:

Step # What to do
1 Add or subtract the whole numbers.
2 Add or subtract the fractions.

## Adding and Subtracting Mixed Numbers – Examples

The first ingredient on the recipe is glue. It says to add three and two-eighths plus four and five-eighths. What is that in total? Let’s start by adding three and two-eighths and four and five-eighths.

First, we need to find the sum of the whole numbers. That means, we are adding three and four first to get the sum of seven.

Next, we find the sum of the fractions.
Remember: When adding and subtracting fractions with common denominators, we simply add or subtract the numerators and the denominators stay the same. Here, this means two-eighths plus five-eighths equals seven-eighths.

Our last step is to simplify our answer if we need to. A fraction is in simplest form when the numerator and denominator have no common factors other than one. Since seven and seven-eighths is in simplest form we can skip this step.

What is the next ingredient on the slime recipe? Now, we have to add five and three-fourths minus four and one-fourth of baking soda. So let’s practice subtracting mixed numbers by calculating five and three-fourths minus four and one-fourth.

First, we need to find the difference of the whole numbers. That means, we are subtracting five and four first to get the difference of one.

Next, we find the difference of the fractions. Three-fourths minus one-fourth equals two-fourths.

Our last step is again to simplify our answer if we need to. The numerator and the denominator have the common factor of two, which means it can be simplified to one-half.

## How to Add and Subtract Mixed Numbers – Summary

Remember to follow the three steps below whenever you add and subtract mixed numbers with like denominators.

• Step 1: Find the sum or the difference of the whole numbers.
• Step 2: Find the sum or the difference of the fractions.

The last step in our recipe is to add one and one-third plus two and two-thirds of contact lense solution. Can you calculate how much that is in total?
The answer is... four! Well done. If you would like to practice some more to optimize your slime, take a look at the exercises and worksheets about adding and subtracting mixed numbers. Enjoy!

## Adding and Subtracting Mixed Numbers exercise

Would you like to apply the knowledge you’ve learned? You can review and practice it with the tasks for the video Adding and Subtracting Mixed Numbers.
• ### Can you find the mixed numbers?

Hints

Is it made up of a whole number and a fraction?

Remember, a mixed number is made up of a whole number and a fraction.

Solution

These are the mixed numbers! Remember, a mixed number is made up of a whole number and a fraction.

Not mixed numbers

5 and 13 are whole numbers.

$\frac{9}{10}$ and $\frac{5}{7}$ are fractions.

• ### Can you sequence the number sentence correctly?

Hints

This is a subtraction problem so the order is important.

Have a look at this fraction. If you divide both the numerator and the denominator by 2, what do you get?

Solution

This is how the number sentence should read.

First of all we subtract the whole numbers so 3 - 1 = 2.

We then subtract the fractions so $\frac{3}{4}$ - $\frac{1}{4}$ = $\frac{2}{4}$.

We then simplify if we need to which in this case we can. $\frac{2}{4}$ can be simplified to $\frac{1}{2}$ by dividing both the numerator and the denominator by two.

We then put the whole number and the fraction together to get our answer of 2$\frac{1}{2}$.

• ### Can you find out how much of each ingredient Axel and Tank need to make gloop?

Hints

Can it be simplified?

Add or subtract the whole numbers first.

Don't forget to double check if it is an addition or subtraction problem.

Add or subtract the fractions next.

Solution

These are the correct answers. Remember to:

• Check whether it is an addition or subtraction problem.
• Add or subtract the whole numbers first.
• Add or subtract the fractions next.
• Simplify if you can.
• ### Can you find the equivalent fractions?

Hints

Remember, you always divide the numerator and the denominator by the same number.

In this example we can simplify $\frac{3}{6}$ to $\frac{1}{2}$ by dividing both the numerator and denominator by 3.

What do you get if you half the denominator on the top row? Or divide it by 3?

Solution

In the example above both the numerator and the denominator have been divided by two to simplify the fraction.

You need to divide the denominator and the numerator by the same number to simplify the fraction. This may be by two or by three or by another number.

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Using the information above, the answers to the other problems are:

• $5\frac{8}{10}$ = $5\frac{4}{5}$ - both divided by two.
• $5\frac{3}{9}$ = $5\frac{1}{3}$ - both divided by three.
• $5\frac{12}{16}$ = $5\frac{3}{4}$ - both divided by four.
• ### Can you find out how much shaving foam Axel and Tank need to make more slime?

Hints

Remember to add the whole numbers first.

When the denominators are the same, we only need to add the numerators.

Solution

If we add the whole numbers first we get 3.

Adding the fractions next gives us $\frac{2}{3}$; we cannot simplify this any further.

• ### Can you check Axel and Tank's alternative recipe for slime?

Hints

Remember to add or subtract the whole numbers first.

Add or subtract the fractions next.

Can the fraction be simplified?

Solution

• The first number sentence was incorrect.
The answer should be 9$\frac{3}{4}$.

3 + 6 = 9

$\frac{5}{8}$ + $\frac{1}{8}$ = $\frac{6}{8}$ which can be simplified to $\frac{3}{4}$.

We put the whole number and the fraction together to get the answer.

• The second problem was correct!
4 + 4 = 8

$\frac{7}{9}$ + $\frac{2}{9}$ = 1.

8 + 1 = 9.

• The third number sentence was also incorrect.
The answer should be 3$\frac{4}{7}$.

10 - 7 = 3.

$\frac{6}{7}$ - $\frac{2}{7}$ = $\frac{4}{7}$.

This cannot be simplified further so put the whole number and the fraction together to get the answer.

• The fourth number sentence was correct!
11 - 5 = 6.

$\frac{7}{8}$ - $\frac{3}{8}$ = $\frac{4}{8}$ which can be simplified to $\frac{1}{2}$.

Put the whole number and the fraction together to get the answer.