1.5Measurement

AS 91030

Perimeters of Polygons

• I can find the length of missing sides• I can find the perimeter of polygons

LEARNING OBJECTIVES

Perimeters of Polygons

A polygon is a shape with straight edges

The perimeter is all the way round the outside

Keywords

Perimeters of Polygons

Perimeter = 6 + 4 + 6 + 4 = 10 cm Perimeter

= 17 + 17= 34 cm

Perimeter = 6 + 5+ 10 + 5

=26 cm Perimeter =

15+15+15+15+15=75 cm

6 cm

4 cm

5 cm

12 cm

6 cm

10 cm

5 cm5 cm 15 cm

5 cm

12 cm

8 cm

3 cmPlan A

Find the missing sides and add everything up (click and they appear)7 cm

5 cm Perimeter = 12 + 8 + 3 + 7 + 5 + 5 = 40 cm

Plan B

Click for cool animation to see the problem a different way

So now we have a rectangle and the perimeter = 12 + 8 + 12 + 8 = 40 cm

8 cm

12 cm

90 cm

120 cm

Find the total length of black lines.

side edge 2 x 120 cm lines = 240 cmtop 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

Total length of black lines = 4 x 120 + 4 x 90 = 840 cm

• I can find the length of missing sides• I can find the perimeter of polygons

SUCCESS CRITERIA