Probability-primary mathematics
Probability
Probability is the likelihood or chance of an event occurring.
Many events can’t be predicted with total certainty. The best we can say is how likely they are to happen, using the idea of probability.
Tossing a Coin
When a coin is tossed, there are two possible outcomes:
- heads (H) or
- tails (T)
We say that the probability of the coin landing H is ½
And the probability of the coin landing T is ½
Throwing Dice
When a single die is thrown, there are six possible outcomes: 1, 2, 3, 4, 5, 6.
In general:
Example 1:
What is the chances of rolling a “4” with a die
Number of ways it can happen: 1 (there is only 1 face with a “4” on it)
Total number of outcomes: 6 (there are 6 faces altogether)
Example 2:
There are 5 pens in a bag: 4 are blue, and 1 is red.
What is the probability that a blue pen gets picked?
Number of ways it can happen: 4 (there are 4 blues)
Total number of outcomes: 5 (there are 5 marbles in total)
The probabilities lie between 0 and 1
(i) The probability of something which is certain to happen is 1. For example, the probability that the sun will rise from the east tomorrow is 1
(ii) The probability of something which is impossible to happen is 0. For example the probability that man has four eyes = 0
(iii) The probability of something not happening is 1 minus the probability that it will happen.
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