1TH/Vwo §7.6 Calculating with percentages.

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

Some explanations and a few tasks for you too!

Who could explain the joke of this joke?

write 33 % as a fraction

explanation:

33 %  is  33 of 100, so  it is:

Common mistake:

33 % =  

This is wrong, because :

                                             %

​100​​33​​

​3​​1​​

​3​​1​​=33​3​​1​​

66 % =

​3​​2​​

​..​​..​​

1. 1/3
2. 2/3
3. 3/4
4. 4/5

FOTOVRAAG:      write as a percentage:

A difficult one!

1st    COPY this task in your Notebook

2nd  WORK it Work out in your Notebook.

3rd  Take a pic of YOUR WORK and 

4th   Send it in in the next slide.

Who will be succesful?!

= ............ %

​250​​82​​

written as a percentage:

This is the same as :

82 x 4     divided by        4 x 250 = 1000,  so it is

, which is the same as                              

 , so the answer is:

32.8 %  !

​250​​82​​

​1000​​328​​

​100​​32.8​​

The final exercise is about the relations between

decimal numbers, percentages and fractions.

Write 92.5 % as a decimal number:

1. 9.25
2. 92.5
3. 0.925
4. 0.93

Explanation:

92.5 %  is the same as 92.5 of 100, or:

0.925

The method here is: 

from a percentage to a decimal number means replacing the point

two places to the left! Just like: 25 % is 0.25

Homework time

Make §7.6 now.