Mathematics

1. Powers of ten
megax 1 000 000 x10⁶xxx kilox 1000 x10³xxx centix 0.01 x10^-2xxx millix 0.001 x10^-3xxx
micro x0.000 001 x10^-6xxx nanox0.000 000 001 x10^-9xxx pico x0.000 000 000 001 x10^-12

2. Division by decimals
8/0.1 = 80 6.7/0.1 = 67xxx 50/0.2 = 250 xxx24/1.2 = 20xxx 4/0.001 = 4000

3. Algebra
Pythagoras' theorem
For a right angled triangle:
(Hypotenuse)² = (Opposite)² + (Adjacent)²

4. Trigonometry
sin A = Opposite/Hypotenusexx
cos A = Adjacent/Hypotenuse xx tan A = Opposite/Adjacent

5. Changing the subject
V = IR, I = V/R and R = V/I are just different ways of writing the same equation
The top letter is found by multiplying the two lower letters.
Either of the two lower letters is found by dividing the top letter by the other lower letter

6. Useful areas and volumes
Area of a circle = pr²xxx Area of the surface of a sphere = 4pr²xxx Volume of a sphere = 4/3 pr³xxx Volume of a rectangular solid = length x width x heightxxx Area of a triangle = ½ base x height