Formulas and rules
Every key math formula and rule, organised by topic and school level, with examples and study tips.
Geometry 7
Perimeter and area
perimeter = sum of sides; rectangle area = l x w
Perimeter is the distance around a shape, area is the surface inside it.
Area of a triangle
area = (base x height) / 2
Half the base times the perpendicular height.
Circle area and circumference
area = pi r^2 ; circumference = 2 pi r
Pi is roughly 3.14. The diameter is twice the radius.
Angle rules
triangle = 180 deg; straight line = 180 deg; full turn = 360 deg
Angles in a triangle add to 180. On a straight line they add to 180. Angles at a point add to 360.
Volume
box = l x w x h; cylinder = pi r^2 h
Volume measures the space inside a solid, in cubic units.
Symmetry
A shape has a line of symmetry when it folds exactly onto itself.
Coordinates
A point (x, y) gives the horizontal then vertical position. x comes before y.