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 )