# 1819 G2X §4.4

Which exercises/theories should I discuss on the board?
1 / 10
Slide 1: Mind map
WiskundeMiddelbare schoolhavo, vwoLeerjaar 2

This lesson contains 10 slides, with interactive quiz and text slides.

Lesson duration is: 50 min

## Items in this lesson

Which exercises/theories should I discuss on the board?

#### Slide 1 -Mind map

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.

#### Slide 2 -Slide

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

Sketch

Calculations

#### Slide 5 -Slide

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

The scale factors are:
B: 2
C: 3
D: 4

#### Slide 6 -Slide

Scale factor and area
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 7 -Slide

Scale factor and area

The area is multiplied by the scale factor squared!

#### Slide 8 -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 9 -Slide

Homework Tuesday
• 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