Probability

A big subject but follow a few simple rules and it is fairly easy
to work out probabilities.

Certainty is represented by 1
No chance at all is represented by 0

Usually our chances of an event occuring are somewhere between 0 and
1 and our job is to find out what that chance is. Probability often uses
fractions
Example what is the chance of throwing a three with a six sided dice.
Well the chance of it landing on any one side is one sixth =1/6 so the
chance of landing on a three is 1/6

How about this example.
There is a six sided dice, what is the chance of throwing a three and
then a two
Chance of throwing a three on the first throw is 1/6
Chance of throwing a two on the second throw is 1/6
So the chance of throwing a three then a two is = 1/6 X 1/6 =1/36
I.e a 1 in 36 chance

Take a look at the youtube video

http://www.youtube.com/watch?v=sqk1-q8gXcY
Can you work out the chance of putting five numbers in the right order?

Answer
Chance of picking the first number is 1/5
second number is 1/4 (because there are only four numbers left)
third number is 1/3
fourth number is 1/2
and last is 1/1 or certainty as it is the only number left

So probability = 1/5 X 1/4 X 1/3 X 1/2 X 1/1 =1/(5X4X3X2X1) =1/120
But in the video it is not that simple as we would not choose the '0'
as our first number.

taking this into account the probability is really =
1/4 X 1/4 X 1/3 X 1/2 X 1/1 =1/96