Which exercises/theories should I discuss on the board?

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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.

Slide 3 - Slide

Sketch

Slide 4 - Slide

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 )