1TH/Vwo §8.5 multiplying fractions

• Wiskunde
• Middelbare school
• havo, vwo
• Leerjaar 1

§8.5 Multiplying fractions

After   +       and        -     we now look at

the operation:       x   !

By the way, this is a pretty long LessonUp.

The Homework however is only 3 exercises.

First we multiply a fraction by a whole number:

Now it's your turn:

​3​​2​​

x 33 = ...

solution:

another one for you:

3/13 x 52 = ....

1. 10
2. 9
3. 14
4. 12

Solution:

Now let's talk business:

Finally it's

Fraction times Fraction ...

2 Important points:

.                        and               .

an even more important point is this:

 COMMON MISUNDERSTANDING; somebody tries to tackle the task below :

 ' Wait a sec, the new denominator is 14 x 4, but then it's still a long way....

              

                x            =         x          =                          x                         ??? I am at a loss...'

​14​​13​​

​4​​3​​

​56​​52​​

​56​​42​​

​.......​​......​​

​........​​.......​​

Why does this method really suck?

SOLUTION:

  When multiplying fractions with unequal denominators,

    you don't have to make them equal!!

Watch the next slides that show how simple it really is!

your turn again:

3/8 x 3/8 = ...

1. 9/8
2. 9/64
3. 6/16
4. 3/64

Solution:

Fotovraag: first work it out in your Notebook, take a pic and send in in next slide!

 Show your CALCULATION!

Don't forget to SIMPLIFY your answer, in the end!

2/7 + 1/7 x 1/2 = ......

Solution:

Now it's time for a complicated one:

Think about HOW to WORK it out!

 After that we look at the solution.

This is the Solution:

For example this one.                                   You might think:

2  x  3 = 6      and                 x          = 

So the final answer is:        6   +        =   6                 However this is WRONG!

​2​​1​​

​4​​1​​

​8​​1​​

​8​​1​​

​8​​1​​

Let's look back at the previous slide for a sec to see if both methods are good!

Fotovraag:

again work it out in your Notebook first and then send it in.

1 1/8 x 1 1/3 = ......

Solution:

Homework:

§8.5 Make only these tasks:

40, 42, 44 and 45. (you've done so much already!)

Send in your CALCULATIONS.

NOTE:  Showing only the answers has no value.

It's about WRITING DOWN the process in LITTLE STEPS!