There is a one in two chance of getting heads when a coin is tossed. When
a coin is tossed you can get either a head or a tail. So there are 2 possible
outcomes. But if we want heads then only 1 outcome is successful. So we want
1 outcome out of the 2 possible outcomes. We can write this as a fraction
.

Every probability can be written as a fraction.

Remember: The smaller the fraction the less likely it is that the event will
happen.

Example 1:

In lottery numbers, it is possible to work out that there are 13 983 816 ways
to choose 6 numbers from 1 to 49. There is only one winning combination. What
is the probability as a fraction?

To make a fraction you put the number of successful outcomes on top. That's
a 1. Then put the total number of possible outcomes on the bottom. That's
13 983 816.

So the fraction is = 1 in 14 million. As this is a very small amount it is
unlikely to happen.

Example 2: By looking at the statistics for accidents insurance companies
work out a probability for them happening again. The probability of being
killed in a plane crash has been found to be 11 million to 1, a very small
probability.

**Next : Probability of Either of Two Events **

**Previous : Combination**