Probability of Combined Events
Probability
A measure between 0 and 1 of how likely an event is to happen.
| English | Probability |
|---|---|
| Bahasa Melayu | Kebarangkalian |
| 中文 | 概率 |
How it is used
A bag holds 3 red and 5 blue marbles. The probability of drawing a red marble is P(red) = 3/8 = 0.375, since there are 3 favourable outcomes out of 8 equally likely ones.
Where it shows up in SPM
The foundation of the whole Probability of Combined Events chapter, and used again in statistics questions. In Paper 1 it appears as a quick multiple-choice or short-answer value; in Paper 2 it opens a longer structured question before you combine events with tree diagrams or tables.
Don't confuse it with
Open the chapter: Probability of Combined Events →
Frequently asked questions
Can a probability be more than 1?
No. Every probability lies between 0 and 1 inclusive.
A value of 0 means the event is impossible and 1 means it is certain. If your working gives an answer above 1, such as 5/3, you have made an error, usually by using the wrong total in the denominator.
Do I write the answer as a fraction or a decimal?
Either is accepted, but keep the fraction in its simplest form, for example 3/8 rather than 6/16. Only round to a decimal if the question asks for it, and keep at least three significant figures so you do not lose accuracy in later steps.
What does 'equally likely' mean and why does it matter?
It means each outcome has the same chance, like each face of a fair die. The formula P(A) = number of favourable outcomes over total outcomes only works when outcomes are equally likely, which is why SPM questions say 'fair' die or coin.