Science, Maths & Technology

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Everyday maths 1

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9.1 Probability scales

In real life, things usually fall somewhere in between the two extremes of ‘will never happen’ and ‘will definitely happen’.

We can use a probability scale to measure how likely events are to occur:

Figure _unit4.9.1 Figure 13 A probability scale
• The probability of an impossible event (‘will never happen’) is 0.
• The probability of a certain event (and ‘will definitely happen’) is 1.
• All other events come between 0 and 1.
• Events with an even chance have a probability of .

Now try the following activity, where you’ll need a ruler and a pencil. Remember to check your answers once you have completed the questions.

Activity _unit4.9.2 Activity 15: Looking at probability

Use a ruler to draw your own probability scale. Mark on it 0, 1/2 and 1. Label 0 as ‘impossible’ and 1 as ‘certain’.

Then mark these statements on the probability scale with crosses and label them with their question letter:

• a.The probability that the sun will rise tomorrow.
• b.The probability that you will run the London Marathon next year.
• c.The probability of dying one day.