# 2TH §3.4 Calculating using similarity

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

This lesson contains 11 slides, with interactive quiz and text slides.

Lesson duration is: 50 min

## Items in this lesson

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

#### Slide 1 -Slide

§3.4: S25, 27, S28

#### Slide 4 -Slide

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 5 -Slide

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 6 -Slide

Scale factor and area (2)

The area is multiplied by the scale factor squared!

#### Slide 7 -Slide

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 8 -Slide

Homework
• Do §3.4: Exercise 28, 29, 30
• Do §3.5: Exercise 31