Fractio

nsLet’s

make

fractions

our

friends!

Now, let’snot get all crazy

with this “friend” stuff,Mr. Sunshine.

© Mike’s Math Mall

Multiply

ingPowerPoint

Introduction

Multiplying

Fractions

Hi! Myname is SparkyO’Flannagan!

Psst…it’s not that kind of introduction,

Sparky!Oops!

My bad!

No, sir!I would call itsuper-duper fantabulous,

news!

Iwouldn’t

call that good news!

Multiplying FractionsI know you’re not a big fan of fractions,

Sparky, but I have some good news when it comes to multiplying them.

“Good news”and “fractions” all inthe same sentence?

Impossible!

What if I told you that when we multiply fractions, we don’t have to worry about

making common denominators?

Really? I knew you’dcome around!

Multiplying Fractions 101

When we multiply fractions,we use the multiplication symbol:

×

A raised dot: ∙

Or parenthesis:

Multiplying Fractions 101

Some terms you need to know:

numeratordenominator

Simplify – reduce a fraction to its simplest form using the GCF (greatest common factor)

The GCF of is 4.

Example:

Use the GCF toreduce the fraction!

Multiplying Fractions 101Practice changing improper

fractions into mixed numbers.

𝟏𝟏𝟐𝟓

−𝟏𝟎

𝐫

𝟏

𝟏

Now you try some!

Write 5 with the remainder 1 over

the denominator 2: →

1) 2) 3)

Mixed Number – a whole number combined with a fraction. →

Improper Fraction – a fraction with a numerator larger than the denominator.

Multiplying Fractions 101Practice changing mixed numbers

into improper fractions.

𝟒×𝟑+𝟐𝐨𝐯𝐞𝐫𝟑

Take the whole number times the denominator, add the numerator, and

place over the denominator.

Give it a try!

1) 2) 3)

MultiplyingProper

Fractions

Part 1

Example 1:

To multiply fractions:

Always check to be sure

the product is simplified! is simplified!

I’m findingthis somewhat

interesting. Continue,please!

Multiplying Fractions

Multiplying Fractions

Example 2: Example 3:

Don’t forget to simplify!

Change to a mixed number!

Multiply the following fractions.

Time to Show Your Stuff!

1)

2)

3)

4)

So theanswer is already

simplified?

Crafty Cross-Cancelling

Now, let’s look at a method called cross-cancelling, using a previous problem.

Step 1: Look at the numbers across from each other (diagonal numbers).

Step 2: See if those numbers have a GCF > 1. If so, divide each number by that GCF.

What’s the GCF of 3 and 3? 3What’s the GCF of 2 and 8? 2

1

1

1

4

Yep!

Sparkyapproves but needs

to see more!

It makesthe fraction

numbers smaller and helps simplify

the answer!

Let’s do a side-by-side comparison to see how cross-cancelling makes multiplying fractions easier.

Crafty Cross-Cancelling

Standard Method: Cross-cancel method:

1 3

4 4

You sound like a math teacher, Sparkles!I agree!

I hate to admit it, but

this cross-cancellingthingy is kinda

sweet!

This isnot going to

go over well withthe ladies!

MultiplyingMixed

Numbers

Part 2

Multiplying Mixed NumbersBefore we can multiply mixed

numbers, we need to change them into improper fractions.

Example 1:

2

11

4

¿8This looks

like it might be agood time to use

some of that fancy cross-

cancelling!

Great idea, chief!

Multiplying Mixed NumbersExample 2:

I’m reallystarting to wig

out here!

What’s wrong, Sparkington?

All thisjunk is actually

starting to make sense!

But isn’t that a good thing?

I’mnot used to

things making sense…Need

air now!

We better practice!

Show us how it’s Done!Multiply the following mixed numbers.

1)

2)

3)

¿11 1

1

1

7

2

3

Fantastical!But I’m starting to get

a little worried.

BecauseI think I actually wanna start becoming friends

with fractions!

© Mike’s Math Mall

Multiplying FractionsSo, how did it go with the mixed

numbers, Sparky?

Oh, really?And why’s that?

That’s just weird, Mr. Sunshine!