Add/Subtract Fractions

Add/Subtract Fractions

Review Format

• Mini-Lesson

• Review Question

• Solution

Mini-Lesson

Step 1 - Find a common denominator (least common multiple)

Step 2 - Write equivalent fractions using the common denominator

Step 3 - Add/Subtract the numerators only. Keep the denominator the same all the way through

Step 4 - Simplify if possible

Fill in the Blanks

Bob has a stamp collection. He wrote what states the stamps are from.

Indiana       ⅙  
California     ⅓
South Dakota   ⅓
Florida         ⅙

What fraction of Bob’s stamps came from California, Florida, or Indiana?

Solutions

Solution 1

Since South Dakota is the only state not listed, then you can subtract South Dakota's 1/3 from the whole 1, which leaves the rest to be 2/3.

Solution 2

You could add California, Florida, and Indiana's fractions together. 1/3 + 1/6 + 1/6

Use a denominator of 6, so 1/3 = 2/6

2 + 1 + 1 = 4, so 4/6, which can be simplified by dividing each number by 2. 4/6 = 2/3

Mini-Lesson

When given a diagram of a fraction, write down what fraction the diagram represents and then solve the problem.

Fill in the Blanks

Solution

1/3 + 1/4 Common denominator is 12

4/12 + 3/12 = 7/12

Mini-Lesson

Pay close attention for the word NOT.

That means you find what IS, and then subtract it from 1.

You do that by making the common denominator to be both the numerator and the denominator.

1 = 5/5 or 1 = 12/12 or 1 = 6/6

Fill in the Blanks

Mr. Brewer and Mr. Cowden were eating pizza. Mr. Brewer ate  $\frac{3}{12}$   of the pizza. Mr. Cowden ate  $\frac{3}{6}$   of the pizza. What fraction of the pizza was NOT eaten?

Solution

Find what IS eaten.

3/12 + 3/6 Common denominator is 12

3/12 + 6/12 = 9/12

1 - 9/12 You have to make the one a fraction

12/12 - 9/12 = 3/12

Simplify - 3/12 = 1/4

You've Got This!

Do the next two on your own.

Fill in the Blanks

Solution

3/4 - 1/3 The common denominator is 12

9/12 - 4/12 = 5/12

Fill in the Blanks

Sally had 1 gallon of milk. She used  $\frac{1}{5}$   of a gallon of milk to make pudding.  She used  $\frac{1}{10}$   of a gallon to bake oatmeal.  How much of a gallon of milk did she use?

Solution

1/5 + 1/10 The common denominator is 10

2/10 + 1/10 = 3/10

It cannot be simplified.

There will be a mini-test tomorrow over these kinds of problems.

Adding & Subtracting Fractions