# 2Tvwo § 4.4 Calculating using similarity

§ 4.4 Calculating using similarity
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Slide 1: Tekstslide
WiskundeMiddelbare schoolhavo, vwoLeerjaar 2

In deze les zitten 14 slides, met interactieve quiz en tekstslides.

Lesduur is: 50 min

## Onderdelen in deze les

§ 4.4 Calculating using similarity
That's the content for today!

#### Slide 1 -Tekstslide

Calculating unknown sides in similar figures
When calculating unknown sides in similar figures, you can use the scale factor (see LessonUp §4.2).

To make it easier to find out which sides are corresponding sides, you should sketch both figures in the same position.
Watch the following example!

#### Slide 2 -Tekstslide

Example
Triangle ABC and triangle PQR are similar figures. Calculate the length of AC and PR.

#### Slide 3 -Tekstslide

Sketch
Here a better sketch
Now the triangles
are in the same position.

Calculations

#### Slide 5 -Tekstslide

Before we go on ...
here comes a non-math slide !

#### Slide 7 -Tekstslide

Scale factor and perimeter
Perimeter rectangle A = 2 + 1 + 2 + 1 = 6 cm

Perimeter rectangle B = 4 + 2 + 4 + 2 = 12 cm
Perimeter rectangle C = 6 + 3 + 6 + 3 = 18 cm
Perimeter rectangle D = 8 + 4 + 8 + 4 = 24 cm

12 = 6 x 2; 18 = 6 x 3; 24 = 6 x 4.
The perimeter is multiplied by the scale factor.

#### Slide 8 -Tekstslide

Scale factor and area (1)
Rectangles B, C and D are
enlargements of rectangle A.

The scale factors are:
B: 2 (meaning: when you
multiply length and width of picture
A by 2, you get picture B)
C: 3
D: 4

#### Slide 9 -Tekstslide

Scale factor and area (2)

The area is multiplied by the scale factor squared!

#### Slide 10 -Tekstslide

Scale factor and area
When the dimensions (length/width/height) of a figure are multiplied by a factor s, the perimeter is also multiplied by s, but the area is multiplied by      .

(When you learn about volume you will find that the volume is multiplied by      )
s2
s3

#### Slide 11 -Tekstslide

Homework
• Make §4.4:
Support: 24, 25, S26, 27, S28, 28, 29
Standard: 24, 25, 26, 27, 28, 29, 30
Challenge: 24, 26, 27, 28, 29, 30, C5