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