Multiplying Fractions

5th GradeMrs. Mitchell

Vocabulary Week 3

• Reciprocal – the fraction you get once you turn the fraction upside down, meaning the numerator becomes the denominator and the denominator becomes the numerator. Ex: 2/3 is the reciprocal of 3/2.

• Product – the answer to a multiplication problem.

• Improper Fraction – fraction where the numerator is larger than the denominator

Math Drill – 5 Minute Frenzy

http://www.online-stopwatch.com/

Reciprocals & Canceling

Multiplying and Dividing Fractions

What is a reciprocal?The fraction you get once you turn the fraction upside down.

http://www.mathsisfun.com/reciprocal-fraction.html

Fraction Reciprocal

3/8

5/6

1/3

19/7

Reciprocal of a Fraction

To get the reciprocal of a fraction, just turn it upside down. 

In other words swap over the Numerator and Denominator.

Examples:

Reciprocal of a Mixed Fraction

To find the reciprocal of a Mixed Fraction, we must first convert it to an Improper Fraction, then turn it upside down.

Example: What is the reciprocal of 2 1/3 ?

1. Convert it to an improper fraction: 2 1/3 = 

2. Turn it upside down: 

The Answer is: 

What pattern do you see?

• 2/3 x 3/2 = 6/6 = 1

• 1/2 x 2/1 = 2/2 = 1

• 5/6 x 6/5 = 30/30 = 1

So what rule can we write?

LET’S PRACTICE

http://www.mathsisfun.com/reciprocal-fraction.html

Canceling to Solve Fraction Multiplication Problems

Rules for Multiplying Fractions

There are 3 simple steps to multiply fractions:

• 1. Multiply the top numbers (the numerators).

• 2. Multiply the bottom numbers (the denominators).

• 3. Simplify the fraction if needed.

Let’s add “canceling whenever possible’, where could we add this step in the list above?

Let’s Practice…

http://www.mathplayground.com/fractions_mult.html

Homework for Agenda:

Math Worksheet – Front and Back, Even Numbers only

- Using Canceling to Multiply Fractions

- Finding Reciprocals

Give me the sum of 2/3 and its reciprocal.