3. State the letter you think best represents the following events on the number line.
(i) An event that is impossible
(ii) An event that has an even chance of happening
(iii) An event that is certain to happen
(iv) An event that is very likely to happen
(v) An event that is unlikely to happen (vi) An event that is likely to happen
0 A
B C D 0.5 E F 1
Taking it FURTHER
4. Assign a probability value to the following events. In each case, justify your answer.
(i) The sun will rise in the north. (ii) Saint Patrick’s Day will be in March. (iii) If I toss a coin, it will land on tails.
(iv) If you roll two standard dice, you will obtain a score of zero.
(v) A natural number chosen at random will be even. (vi) A person will have a birthday on the 32nd of June.
5. Think of an event that would have the following probability.
(i) 0⋅5 (iii) 70%
(ii) 2 (iv) 5
__ 7
__ 6
6.2 Calculate the probability of a single event
In experiments involving chance, we must use the correct language to accurately describe what we are doing and the results obtained.
An experiment or trial is the event or action of doing something and recording results, e.g. tossing a coin, rolling a dice, choosing a marble from a bag, etc.
By the end of this section you should:
● be able to list all possible outcomes of an experiment
● understand how to calculate basic single event probabilities
An outcome is a possible result of an experiment or trial.
Probability of an event happening When there are multiple outcomes to a trial, the probability of an event occurring P(E) is
P (E) = number of outcomes favourable to that event _________________________________ number of possible outcomes
Worked example 1 Calculate the probability of rolling the number 3 on a standard die.
Solution
Section A Introducing concepts and building skills