Post on 17-Jan-2016
Mensuration
ObjectivePerimeter and area of shapes made
from triangles and rectangles
Does anybody know what perimeter is?The perimeter of a shape is all the way around the shape.
3cm
3cm
3cm
3cm
Perimeter =3+3+3+3 = 12cm
Pick a starting point!
Don’t forget units!
On your white boards find the perimeter of
these shapes…
8cm
16cm
12cm
10m
10m
4m4m
28m
8m
10m
5m
2m
3m
8m
5m
51m
4mm
10mm
5mm
6mm
42mm
Does anybody know what area is?
Area is the amount of space inside a shape.
Area of a rectangle
length
width
Area of a rectangle = length x width
ExampleFind the area of this rectangle
5cm
3cm
Area = length x widthArea = 5cm x 3cmArea = 15cm²
Don’t forget the correct units!
On your white boards find the area of these
rectangles…
10cm6
cm
60cm²
2mm
12
mm
24mm²
23km
2k
m
46km²
2m8
2cm
1.64m² or 16400cm²
Area of a triangle
Length
Heig
ht
---------------------------------------------------------------
Area = length x height_____________ 2
ExampleFind the area of this triangle
5c
m
8cm
Area = length x height
_____________ 2
Area = 8cm x 5cm__________ 2
Area = 20cm²
On your white boards find the area of these
triangles…
10
m
10m
50m²
6m
9m
27m²
3km
5km
Perpendicular height
7.5km²
10m
m 8m
m
9mm
8m
m
36mm²
Could you find the area of this shape?
10cm
12
cm
5cm
6cm
30cm²
4cm
48cm²
Area = 30cm² + 48cm²Area = 78cm²
10m
14m
5m
Could you find the area of this shape?
50m²
4m5
m 10m²
Area = 50m² + 10m²Area = 60m²