1. 1.5 Measurement
AS 91030

2. Perimeters of Polygons
Learning objectives
I can find the length of missing sides
I can find the perimeter of polygons

3. Perimeters of Polygons
Keywords
A polygon is a shape with straight edges
The perimeter is all the way round the outside

4. Perimeters of Polygons
5 cm
6 cm
Perimeter = = 10 cm
Perimeter =
= 34 cm
4 cm
12 cm
6 cm
Perimeter =
=26 cm
Perimeter =
=75 cm
15 cm
5 cm
5 cm
10 cm

5. 3 cm
Plan A
Find the missing sides and add everything up (click and they appear)
7 cm
5 cm
Perimeter =
= 40 cm
12 cm
5 cm
8 cm
Plan B
Click for cool animation to see the problem a different way 
12 cm
So now we have a rectangle and the perimeter = = 40 cm
8 cm

6. Find the total length of black lines.
90 cm
side edge 2 x 120 cm lines = 240 cm
top edge 2 x 90 cm lines = 180 cm
inside there are 2 more 120 cm lines (click to see)
and 2 more 90 cm lines which I didn’t animate
120 cm
Total length of black lines =
4 x x 90 = 840 cm

7. Success Criteria I can find the length of missing sides
I can find the perimeter of polygons