Excellent. You clearly understand
probabilities and also fractions.
If even numbers are 3/6 then odd numbers must be 3/6 because
this gives a total of 6/6 which is 1.

A probability of zero means an outcome will never happen.
The chance of it not raining for a whole year in the UK
has a probability of 0.

A probability of 0.5 means there is an equal chance of
an outcome happening or not. Landing heads when flipping
a coin has a probability of 0.5

A probability of 1 means an outcome will definitely happen.
The probability that a brick will sink in a bucket of
water is 1.

Probabilities and outcomes

When an event has more than one outcome, what do the probabilities
of each outcome add up to?

Looking at the roll of a dice:

The probability of throwing a 1 is 1 in 6. This can be
written as 1/6 or 0.1666.

The probability of throwing a 2 is 1 in 6. This can be
written as 1/6 or 0.1666.

Think about the probabilities of rolling a 3, 4, 5, or
6.

So if you look at all the possible outcomes, the total
of all their probabilities must add up to 1. This could
be thought of by saying that it is absolutely definite that
when you roll a dice you wil get a 1 or 2 or 3 or 4 or 5
or 6.

Knowing one probability allows another
to be calculated

Remember that the total of probabilites for a particular
event add up to 1. So what are these probabilities?

Try again.

Remember that the "snow" and "no-snow"
probabilities must add up to 1.

The probability of rolling
an even number on a six-sided dice is 3/6. What is the
probability of rolling an odd number?

Percentage probabilities

Just to make things really tricky, probabilities are
sometimes also quoted in percent. To do this just use
a probability scale that runs from 0% (never happen) to
100% (definitely happen). Remember that the total of all
probabilities must now add up to 100%.