Probabilities are used to describe how likely or unlikely it is that something will happen. Weather forecasters often talk about how likely it is to rain, or perhaps snow, in particular parts of the world.
Note
Assume that any die referred to in this unit is 6-sided and fair. Assume that a coin is fair. A pack of cards comprises 52 cards.Worked Examples
When you roll a die, which number are you most likely to get?
Show meYou are equally likely to get any of the six numbers.
If you rolled a die 600 times how many sixes would you expect to get?
Show meYou would expect to get a six in about of the throws, so 100 sixes.
Would you expect to get the same number of ones?
Show meYes, in fact you would expect to get about 100 of each number.
Use one of the following to describe each one of the statements (a) to (d).
Certain
Very likely
Likely
Unlikely
Very unlikely
Impossible
It will snow in Barbados tomorrow.
Show meImpossible (It will never snow in the Caribbean because of the islands' close proximity to the Equator.)
It will rain in London on Saturday.
Show meLikely or Very likely.
You win a car in a competition tomorrow.
Show meVery unlikely if you have entered the competition. Impossible if you have not entered the competition.
You will be late for school tomorrow.
Show meVery unlikely.
Exercises
