Two happy children at a kitchen table waiting for dinner

Pizza Party Fractions

Maya and her brother Theo share one pizza cut into 8 equal slices. Can fractions tell us how much they ate together?

4th Grade Math

Step 1: Name the Parts

Maya ate 3/8 of the pizza. Theo ate 2/8. Each fraction refers to the same whole pizza. What is the denominator, the bottom number?

The denominator is 8 because the pizza is cut into 8 equal parts. The denominator names the size of the parts, not how many were eaten.

Step 2: Add the Numerators

The parts are the same size, so we add only the top numbers. Each top number is a numerator. How much pizza did Maya and Theo eat together?

3/8 + 2/8 = ?

3/8 + 2/8 = 5/8. Add the numerators: 3 + 2 = 5. The denominator stays 8 because the slices did not change size.

Step 3: How Much Is Left?

The whole pizza is 8/8. Maya and Theo ate 5/8. Subtract to determine the leftover part.

8/8 - 5/8 = ?

8/8 - 5/8 = 3/8. Subtract the numerators: 8 - 5 = 3. The denominator stays 8. Three slices are left!

Let's Remember

Fraction Word Problems

          Step 1: Check that both fractions refer to the same whole.

          Step 2: Decide: joining means add, taking away means subtract.

          Step 3: Add or subtract only the numerators.

          Step 4: Keep the denominator the same.

Analyze each problem before you compute. The story tells you which operation to use.

Watch Out!

A Common Mistake

          3/8 + 2/8 is not 5/16.

          The slices stay the same size, so the denominator stays 8.

The model shows the truth: 5 shaded parts out of 8. That is 5/8.

Your Turn: Ribbon Problem

Jade has 7/10 of a meter of ribbon. She uses 4/10 of a meter to wrap a gift. How much ribbon is left?

Using ribbon means take away, so subtract: 7/10 - 4/10 = 3/10. Numerators: 7 - 4 = 3. The denominator stays 10.

Your Turn: Walking Problem

Ava walks 2/6 of a mile to the library. Then she walks 3/6 of a mile to the park. How far does Ava walk in all?

Joining two distances means add: 2/6 + 3/6 = 5/6. Numerators: 2 + 3 = 5. The denominator stays 6.

What Goes in the Blank?

Omar mixed 5/12 cup of red paint with some blue paint. Now he has 11/12 cup of purple paint. How much blue paint did he add?

5/12 + ?/12 = 11/12

5/12 + 6/12 = 11/12. To find the missing numerator, subtract: 11 - 5 = 6. Omar added 6/12 cup of blue paint.

Your Turn: Water Bottle

0

1/4

2/4

3/4

1

Sam's bottle held 3/4 of a liter of water. He drank 2/4 of a liter at soccer practice. How much water is left?

3/4 - 2/4 = 1/4. Start at 3/4 on the number line and jump back 2 fourths. You land on 1/4.

Your Turn: Garden Problem

Kenji plants tomatoes in 1/5 of his garden. He plants peppers in 3/5 of the same garden. What fraction of the garden is planted?

1/5 + 3/5 = 4/5. Both fractions refer to the same garden. Add the numerators: 1 + 3 = 4. The denominator stays 5.

Challenge! Trail Mix

Noor's jar holds 11/12 cup of trail mix. She pours in 3/12 cup of raisins and 4/12 cup of nuts. How much room is left in the jar?

Two steps! First add: 3/12 + 4/12 = 7/12. Then subtract: 11/12 - 7/12 = 4/12 cup of room left.

Think About It

When could you add or subtract fractions at home? Think about sharing food, measuring for a recipe, or filling a jar. Why must both fractions refer to the same whole?

Great Work!

0/9

correct

fraction numerator denominator analyze determine