Multiplying Fractions

Grade 5 Mathematics

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The Big Idea

To multiply fractions: Multiply the numerators, then multiply the denominators!

No common denominators needed - multiplication is actually EASIER than addition!

Remember: Multiplying by a fraction less than 1 gives a SMALLER answer!

Example 1: Multiply Two Fractions

23 x 14 = ?
1

Multiply the numerators: 2 x 1 = 2

2

Multiply the denominators: 3 x 4 = 12

3

Write your answer: 2/12 = 1/6 (simplified)

23 x 14 = 212 = 16

Example 2: Visual Model (Area Model)

What is 1/2 x 2/3? Let's see it with a picture!

This rectangle is divided into 3 columns and 2 rows (6 total parts)

Shade 2/3 horizontally (2 columns of 3)

Shade 1/2 vertically (1 row of 2)

The overlap (dark purple) = 2 out of 6 = 2/6 = 1/3

12 x 23 = 26 = 13

Example 3: Fraction x Whole Number

Write the whole number as a fraction over 1!

5 x 34 = 51 x 34 = 154 = 334

Key Insight: Multiplying Makes Smaller!

When you multiply by a fraction less than 1, your answer is SMALLER than what you started with.

Why? Because "1/2 x 1/3" means "half OF a third" - you're taking a PART of something!

Think of it as: "What is 1/2 of 1/3?" The answer (1/6) is smaller than both!

TRAP ALERT: Don't Find Common Denominators!

WRONG: Some students try to find common denominators like in addition. You DON'T need to!

RIGHT: Just multiply straight across: numerator x numerator, denominator x denominator. That's it!

Your Turn: Multiply the Fractions

1. 12 x 13 =

Numerators: ___ x ___ = ___   Denominators: ___ x ___ = ___

2. 34 x 25 =

Don't forget to simplify if you can!

3. 4 x 23 =

Hint: Write 4 as 4/1 first!

4. A recipe needs 3/4 cup of sugar. If Maria wants to make 1/2 of the recipe, how much sugar does she need?

Equation: ______ x ______ = ______

Answer: Maria needs ______ cup of sugar.

Remember the Steps!