Adding and Subtracting Fractions 1

Adding and Subtracting Fractions 1

Today's responsibility:

Grab something to write with and something to write on!

The Basics

• Numerator: Top of fraction (dividend)

• Denominator: Bottom of fraction (divisor)

Here's a fun gif.

It's pizza.

The Basics

• Numerator: Top of fraction (dividend)

• Denominator: Bottom of fraction (divisor)

Multiple Choice

Where is the denominator in a fraction?

• The Top

• The Bottom

Multiple Choice

 $\frac{1}{2}$  

What is the denominator?

• 1

• 2

Multiple Choice

 $\frac{3}{4}$  

In which fraction is the numerator greater than 3?

•  $\frac{1}{2}$  

•  $\frac{2}{3}$  

•  $\frac{4}{6}$  

Adding

If denominators are the same, add the numerators.

Denominator does not change.

Multiple Choice

 $\frac{2}{5}+\frac{1}{5}=?$  

•  $\frac{1}{5}$  

•  $\frac{2}{5}$  

•  $\frac{3}{5}$  

•  $\frac{4}{5}$  

Multiple Choice

 $\frac{7}{12}+\frac{3}{12}=?$  

•  $\frac{10}{12}$  

•  $\frac{10}{24}$  

•  $\frac{14}{12}$  

Subtracting

If denominators are the same, subtract the numerators.

Denominator does not change.

Multiple Choice

 $\frac{5}{9}-\frac{2}{9}=?$  

•  $\frac{9}{9}$  

•  $\frac{3}{9}$  

•  $\frac{9}{2}$  

But what happens if the denominators don't match?

We find what is called a "common denominator."

Let's break down that phrase.

We'll be adding  $\frac{1}{2}+\frac{1}{4}=?$  

We need a common denominator.

Responsibility check!

Do you have your pen/pencil and paper?

We'll be adding  $\frac{1}{2}+\frac{1}{4}=?$  

We need a common denominator.

Whatever you do to the bottom, you do to the top!

And whatever you do to the top, you do to the bottom!

Multiple Choice

 $\frac{1}{2}+\frac{1}{4}=?$  

•  $\frac{1}{3}$  

•  $\frac{3}{4}$  

•  $\frac{2}{4}$  

 $\frac{3}{6}+\frac{1}{3}=?$  

We need a common denominator.

Multiple Choice

 $\frac{3}{6}+\frac{1}{3}=?$  

•  $\frac{2}{3}$  

•  $\frac{4}{6}$  

•  $\frac{5}{6}$  

 $\frac{3}{4}-\frac{1}{2}=?$  

One last example!

Multiple Choice

 $\frac{3}{4}-\frac{1}{2}=?$  

•  $\frac{1}{4}$  

•  $\frac{2}{4}$  

•  $\frac{3}{4}$  

We use "equivalent fractions!"

 $\frac{1}{2}=\frac{2}{4}=\frac{3}{6}=\frac{4}{8}=\frac{5}{10}=$  

What's the pattern?

 $\frac{1}{3}=\frac{2}{6}=\frac{3}{9}=\frac{4}{12}=\frac{5}{15}=$  

What is the pattern?

Multiple Choice

 $\frac{1}{2}$  

What is an equivalent fraction?

•  $\frac{1}{3}$  

•  $\frac{1}{1}$  

•  $\frac{2}{4}$  

•  $\frac{2}{6}$