Probability:

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Probability is a mathematical way of describing how likely something is to occur.  For instance what is the chance that the sun will shine tomorrow or what are the chances of throwing a 7 with one die?

Doing experiments involving probability, leads to results which are called the outcome.  

The outcome is the result of a single trial of an experiment.

For example:

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Roll one six sided dice 20 times.  Write the number it lands on using a tally table, and write the frequency of the outcome.  This will be the number of times a specific outcome occurs

We know that a dice is numbered from 1 to 6.

The possible outcomes will be from 1 to 6 only.  The above table shows the outcome of rolling a dice 20 times.

When rolling a dice as in the example above, there will be an equal chance for each number to be rolled.  There are 6 chances of rolling a 1 to 6 on the dice.  

If we can only roll the dice once, the probability of rolling a 1 will be one out of 6. The same rule applies for numbers 2 to 6.

In the example above, we know that the dice has been rolled 20 times, which gives a different outcome.  The number 1, was rolled 4 times, and to write this as a fraction of possibility we can say that there was a 4 out of 20 chance to roll a 1.  

The probability of rolling a 2 was 7 out of 20 chance etc.

We can also ask learners, especially when starting the lesson off with, what the probability of the following will be.  They are only allowed to use "likely" or "unlikely"

• What are the chances that the sun will shine in the morning.  
• What chance do you have to get 100% for a maths test?
• What are the chances to roll a 7 with only 1 die?
• What are the chances that it will rain in the afternoon?

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Learners will say that most of these answers will be likely, except rolling a 7 with only 1 die.  1 Die only has the numbers 1 - 6 on it, so rolling a 7 will be impossible.

Tossing a coin

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When tossing a coin, there will only be 2 outcomes.  The only possible outcomes, is for the coin to land on heads or tails.

In the example below, a coin has been tossed 50 times:

The possible outcomes for heads was 37 out of 50

The possible outcomes for tails was 13 out of 50.

If I toss a coin in the air only once, it will either land on heads or tails, which means there will be 2 possible outcomes.  Because I toss the coin only once, the possible outcome will be 1 out of 2, which is also half a chance that it will land on heads or tails.

To calculate the possible outcomes for an event we can use the following formula: