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Math for Kids23 chapters | 325 lessons

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Lesson Transcript

Instructor:
*Dina Albert*

In this lesson, you will learn how to multiply a fraction by a whole number. You'll work through real-world examples where it's necessary to multiply fractions by whole numbers, then you can test yourself with a short quiz.

Fractions make up a lot of the world around us. They're used in cooking, building structures, drawing, and even shopping. So it's important to know how to multiply fractions with not only other fractions, but also whole numbers.

But before we dive into multiplying fractions by whole numbers, let's review a few important basics about fractions:

- When adding fractions with common denominators, add the numbers on top, which are known as
**numerators**. Leave the**denominator**(the number on the bottom) the same. - When multiplying fractions, multiply all the numerators going across and then all the denominators going across.
**Improper fractions**are fractions where the numerator is bigger than the denominator.

Let's say you are baking cookies and the recipe requires 1/2 cup of sugar for one batch. But you want to make 4 batches. So you would need 4 times the amount of sugar. To figure out how much sugar you need altogether, you could add 1/2 cup 4 times:

A faster method to find this same answer is to turn the whole number (4) into an improper fraction, then multiply it by the 1/2 cup of sugar. To turn a whole number into a fraction, simply make the whole number the numerator, and make 1 the denominator. So, in fraction form, 4 is represented as 4/1. Now, multiply:

When multiplying fractions, multiply all the numerators going across and then all the denominators going across:

You can simplify the improper fraction into a whole number by dividing the numerator by the denominator: 4 / 2 = 2. You need 2 cups of sugar.

Let's look at another example. Say you've made a pizza and cut it into 8 slices. You're giving one slice each to three friends. How much pizza will be eaten all together?

We could solve this problem by adding 1/8 three times:

Or, we could solve this more quickly by multiplying 1/8 by 3. Start by turning the 3 into an improper fraction: 3/1. Now, multiply:

Remember to multiply all the numerators going across and then all the denominators going across:

3/8 of the pizza will be eaten.

Your friend Sally tells you that she's 3/4 of the way to turning 12! How old is Sally? You can find the answer by multiplying with an improper fraction. Start by turning the 12 into an improper fraction: 12/1. Now, multiply:

Remember to multiply all the numerators going across and then all the denominators going across:

You can simplify the improper fraction into a whole number by dividing the numerator by the denominator: 36 / 4 = 9. Sally is 9 years old.

We need to know how to multiply fractions by whole numbers for a variety of reasons, like measuring while cooking and solving riddles about a friend's age. To multiply a fraction by a whole number, start by turning the whole number into an improper fraction. An **improper fraction** is when the **numerator** (the number on top) is higher than the **denominator** (the number on bottom). Then, multiply the two fractions, making sure to multiply all the numerators going across and then all the denominators going across.

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Math for Kids23 chapters | 325 lessons

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- Comparing Fractions: Lesson for Kids
- Equivalent Fractions: Lesson for Kids
- How to Add Fractions: Lesson for Kids
- Fractions Games for Kids
- Fractions to Decimals: Lesson for Kids
- Fractions: Lesson for Kids
- Numerator & Denominator Lesson for Kids
- Decimals: Lesson for Kids
- Multiplying Fractions by Whole Numbers: Lesson for Kids 3:04
- Improper Fractions: Lesson for Kids
- What is a Benchmark Fraction on a Number Line? 3:48
- How to Add Mixed Fractions with Different Denominators
- Multiplying Compound Fractions
- Simplifying Compound Fractions
- Dividing Compound Fractions
- Adding Compound Fractions
- Subtracting Compound Fractions
- How to Subtract Fractions with Variables
- Multiplying Fractions with Like Denominators
- Subtracting Fractions with Like Denominators
- Reducing Fractions: Rules & Practice
- Definition of Simplest Form: Lesson for Kids
- How to Add Fractions with Unlike Denominators
- How to Subtract Fractions with Unlike Denominators
- Rules for Subtracting Fractions
- Rules for Multiplying Fractions
- Rules for Dividing Fractions
- Ordering Fractions on a Number Line
- Locating Fractions on a Number Line
- How to Add & Subtract Two Fractions with Like Denominators
- How to Find Equivalent Fractions on a Number Line
- How to Subtract Mixed Fractions with Unlike Denominators
- Go to Fractions for Elementary School

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