Multiplying Fractions

When multiplying fractions, the first step is to multiply the numerators. The numerators are the numbers on top of the fraction.

Example: 2 ⁄ 5 × 3 ⁄ 4

First, we multiply the numerators to get 2 × 3 = 6

To multiply 2/3 and 5/8, first multiply the numerators to get

• 15

• 24

• 6

• 10

Tags

CCSS.5.NF.B.4

The second step is to multiply the denominators. The denominators are the numbers on the bottom.

Example: 2 ⁄ 5 × 3 ⁄ 4

Multiply the denominators to get 5 × 4 = 20

When you multiply the denominators in 2/3 × 5/8, you get

• 10

• 16

• 24

• 40

Tags

CCSS.5.NF.B.4

After multiplying both the numerators and the denominators, it's time to simplify or reduce your product.

Example: 2 ⁄ 5 × 3 ⁄ 4 = 6 ⁄ 20.

The greatest common factor of 6 and 20 is 2. We divide the top and bottom by 2, which simplifies to 3 ⁄ 10.

What is the reduced product of 2/3 × 5/8?

• 10/24

• 5/12

• 1/2

• 10/12

Tags

CCSS.5.NF.B.4

When multiplying whole numbers by fractions, put the whole number into the same format as the fraction by putting it over one.

Example: 1 ⁄ 8 × 2

1 ⁄ 8 × 2 ⁄ 1

We multiply: 1 × 2 and 8 × 1 to get 2 ⁄ 8.

Simplify 2 ⁄ 8 to 1 ⁄ 4, and there's your answer.

What is 1/6 × 4?

• 1/24

• 2/6

• 2/3

• 4/3

Tags

CCSS.5.NF.B.4

Recipes might call for 1 ⁄ 4 cup of flour or 1 ⁄ 2 tablespoon of vanilla, and if you want to change the recipe to serve a different number of people, you're going to have to multiply fractions.

Serving 5 people instead of 10 means using half as much of each ingredient as the recipe says.

1 ⁄ 2 × 2 ⁄ 3

(1 × 2) / (2 × 3) = 2 ⁄ 6

Simplify to 1 ⁄ 3.

You have a cookie recipe that calls for 1/3 cup of sugar. You want to make 3 times as many cookies by tripling the recipe. How much sugar will you need?

• 1/9 cup

• 1/3 cup

• 2/3 cup

• 1 cup

Tags

CCSS.5.NF.B.4

CCSS.5.NF.B.5

CCSS.5.NF.B.6