Home/Fourth Grade Math/Lesson 143
K-5 friendly lesson
One small step at a time.Read the idea, try the activity, and celebrate each win as you go.

Multiply fractions by whole numbers

Multiplying a fraction by a whole number is like adding that fraction to itself multiple times! It's a shortcut for repeated addition.

Do this: Read the concept below, then try the quiz or activity.

Lesson 143 of 202

Concept

Multiplying fractions by whole numbers is repeated addition!

šŸŽÆ Understanding the Concept:

What does 4 Ɨ 1/3 mean?

It means: 1/3 + 1/3 + 1/3 + 1/3

Visual: [Four 1/3 pieces shaded]

Adding: 1/3 + 1/3 + 1/3 + 1/3 = 4/3

So: 4 Ɨ 1/3 = 4/3 = 1 1/3

šŸ’” The Rule: To multiply a whole number by a fraction: Multiply the whole number by the NUMERATOR Keep the DENOMINATOR the same

Example 1: 3 Ɨ 2/5 = ?

3 Ɨ 2/5 = (3 Ɨ 2)/5 = 6/5 = 1 1/5

Example 2: 5 Ɨ 3/4 = ?

5 Ɨ 3/4 = (5 Ɨ 3)/4 = 15/4 = 3 3/4

šŸ” Step-by-Step:

Solve: 6 Ɨ 2/3

Step 1: Write the whole number over 1: 6/1 Ɨ 2/3 Step 2: Multiply numerators: 6 Ɨ 2 = 12 Step 3: Multiply denominators: 1 Ɨ 3 = 3 Step 4: Write answer: 12/3 Step 5: Simplify: 12/3 = 4

šŸŒŸ Number Line Model:

3 Ɨ 1/4 on a number line:

0----1/4----2/4----3/4----1
     ā†‘       ā†‘       ā†‘
   1st    2nd    3rd

Three jumps of 1/4 = 3/4

šŸŽØ Real-World Thinking:

Problem: You have 4 friends. Each friend eats 2/5 of a pizza. How much pizza total?

4 Ɨ 2/5 = (4 Ɨ 2)/5 = 8/5 = 1 3/5 pizzas

Problem: A recipe calls for 3/4 cup flour. You want to make 5 batches. How much flour?

5 Ɨ 3/4 = 15/4 = 3 3/4 cups

šŸ’­ Why Multiply the Numerator? When you have 3 groups of 2/5, you have: ā€¢ 2/5 + 2/5 + 2/5 = (2+2+2)/5 = 6/5

The denominator (5) stays the same because the piece size doesn't change!

Try it

Practice multiplying fractions by whole numbers!

šŸ“ Multiply: 1. 2 Ɨ 1/4 = ? 2. 3 Ɨ 1/5 = ? 3. 4 Ɨ 2/3 = ? 4. 5 Ɨ 3/4 = ?

šŸ”¢ Solve and Simplify: 5. 6 Ɨ 1/2 = ? 6. 3 Ɨ 4/5 = ? 7. 2 Ɨ 5/6 = ? 8. 4 Ɨ 3/8 = ?

šŸŽÆ Convert to Mixed Numbers: 9. 5 Ɨ 2/3 = ? (write as a mixed number) 10. 7 Ɨ 3/4 = ? (write as a mixed number)

šŸ† Word Problems: 11. Each student needs 2/5 yard of ribbon. If there are 8 students, how much ribbon is needed total?

12. A recipe for one smoothie uses 3/4 cup of yogurt. How much yogurt is needed for 6 smoothies?

13. Each lap around the track is 1/4 mile. If you run 12 laps, how many miles did you run?

šŸ’Ŗ Challenge: 14. If 4 Ɨ ?/5 = 8/5, what fraction goes in the box? 15. Which is greater: 3 Ɨ 5/6 or 4 Ɨ 3/4? Show your work. 16. 10 Ɨ 2/5 = ? (Think: Can you simplify before multiplying?)

šŸŽØ Draw It: 17. Draw a model showing 3 Ɨ 2/4 = 6/4 = 1 2/4 = 1 1/2

Complete & Continue ā†’