5. Perimeter and area
 The perimeter is the distance all the way around the
outside of a 2D shape.
 To work out the perimeter, add up the lengths of all
the sides.
 The area of a 2D shape is the amount of surface
it covers.
 The units for area are cm2 (square centimetres),
m2 (square metres) or km2 (square kilometres).
 To work out the area of a rectangle, multiply
its length (the longer side) by its width
(the shorter side).
6. Symmetry
A 2D shape is symmetrical if a line can be drawn through it so
that either side of the line looks exactly the same. The line is
called a line of symmetry.
Square


Equilateral triangle


Rectangle


Isosceles triangle


Parallelogram




7. 3D shapes
3D shapes have faces (sides), edges and vertices (corners).
The exception is the sphere which has no edges or vertices.




8. Nets of 3D shapes
 The net of a 3D shape is what it looks like if it is opened
out flat. A net can be folded up to make a 3D shape.
 There may be several possible nets for one 3D shape.
Here are some examples.
Net of a cube
Net of a cuboid
Net of a squarebased pyramid
Net of a tetrahedron
Equilateral
A figure having all the sides equal
Quadrilateral
A plane figure having four sides and four angles
Polygon
A closed plane figure having many angles and sides (more than four)
Octagon
A polygon having eight angles and eight sides
Rhombus
An obliqueangled equilateral parellelogram
Heptagon
A polygon having seven angles and seven sides
Dodecagon
A polygon having twelve angles and twelve sides
Hexagon
A polygon having six angles and six sides
Nonagon
A polygon having nine angles and nine sides
Hypotenuse
The side of a right triangle opposite the right angle
Trapezoid
A quadrilateral plane figure having two parallel and two nonparallel sides
Scalene
A triangle with three unequal sides
Isosceles
A triangle with two equal sides
Circumference, diameter and radii are measured in linear units, such as inches and centimeters. A circle has many different radii and many different diameters, each passing through the center. A reallife example of a radius is the spoke of a bicycle wheel. A 9inch pizza is an example of a diameter: when one makes the first cut to slice a round pizza pie in half, this cut is the diameter of the pizza. So a 9inch pizza has a 9inch diameter. Let's look at some examples of finding the circumference of a circle. In these examples, we will use = 3.14 to simplify our calculations. 

Example 1: 
The radius of a circle is 2 inches. What is the diameter? 

Solution: 


= 2 · (2 in) 

= 4 in 








































