1TH/Vwo §5.3 Scale

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

§5.3 Scale

LEARNING GOAL:

how to calculate scale using a ratio table

§5.3 Scale

HOW ?

BY MAKING RATIO TABLES FOR EVERY EXERCISE !!

JUST LIKE IN §5.1 and. §5.2

On the TEST about Ch5 this will be asked from all the time.

§5.3 Scale

Celebrating your birthday, inviting 300 people,

is something done ON A LARGE SCALE.

Vital question for 'scale':

'What does 1 cm in the drawing represent in reality?!'

This drawing could be a map of a town, a country or a 

continent,

but also the drawing of a person, an animal, or whatever.   

Let's look at a few examples!

Vital question for 'scale':

What does 1 cm in the drawing represent in reality?!

This drawing could be a map of a town, 

but also the drawing of an animal, or whatever.   

Let's look at an example!

Example of 'scale':

What is the right scale for the drawing of the weasel?

1. 1 : 7.5
2. 15 : 1
3. 1 : 15
4. 30 : 2

Scale  1 : 15  meaning   1 cm on the drawing

equals 15 cm in reality.

Homework time.

+ Later a few more slides follow!

+  CORRECT the following MISTAKE in your Paper Book:

p.185 C5a. '0.016 mm'  should be '0.016 cm' ! 

Up to now ...

The objects (thingies) were drawn much smaller than they are in real life. However, this is going to change!

Fleas (vlooien) or ticks (teken) are seen under a microscope  or in a biology book much greater than they really are. 

In that way we can see what they really look like!

1. 2 : 8
2. 4 : 1
3. 1 : 4
4. 0.5 : 2

So the scale is     4 : 1  ??!

Shouldn't this result be:

1 : 4 ?

No, watch the next slide!

Did you notice this:

No  matter if the scale is about something smaller or larger than the picture, if possible we always use the number 1 !

So, not          2 : 10    but   1 : 5

However      we write      3 : 2     and  not   1 : 2/3   

No fractions or decimal numbers in a scale !

TRY ONE MORE SCALE TASK now.

ANS

Solution:

1.  2.75 cm = 27.5 mm

2. 27.5 : 5.5 = 5

3. 5 mm in the drawing 

     represents 1 mm in reality, so

4.  scale is.  5 : 1

Homework time

+ Make §5.3 Scale now.

+ Good luck!