What is the formula for probability with equally likely outcomes?

P(event)=\frac{favourable outcomes}{total outcomes}

What is a sample space?

The list of all possible outcomes of an experiment.

What does mutually exclusive mean?

The events cannot happen at the same time.

Why should you list outcomes systematically?

So that no outcome is missed or repeated.

Probability basics and sample spacesIB MYP Maths Standard: Flashcards

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What numbers can a probability take?

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What numbers can a probability take?: Any value from $0$ to $1$ (inclusive).
What is the probability of an impossible event?: $0$
What is the probability of a certain event?: $1$
What is the formula for probability with equally likely outcomes?: $P(\text{event})=\frac{\text{favourable outcomes}}{\text{total outcomes}}$
What is a sample space?: The list of all possible outcomes of an experiment.
How many outcomes are there when you roll two fair dice?: $6\times6=36$
How many outcomes are there when you flip a coin and roll a die?: $2\times6=12$
What is $P(\text{not }A)$ ?: $1-P(A)$
What does mutually exclusive mean?: The events cannot happen at the same time.
What is the rule for $P(A\text{ or }B)$ when $A$ and $B$ are mutually exclusive?: $P(A)+P(B)$
Why should you list outcomes systematically?: So that no outcome is missed or repeated.
A bag has 4 red and 6 blue counters. What is P(red)?: $\frac{4}{10}=\frac{2}{5}$

Exam questions on Probability basics and sample spaces

A bag at a school fair in Nairobi holds 5 red counters, 3 blue counters and 2 green counters. One counter is taken from the bag at random.
Find the probability that the counter is red or green. Give a reason why you can add probabilities.2 marks
Two fair four-sided spinners, each numbered 1 to 4, are spun and the two scores are added together.
Find the probability that the total is at least 7.2 marks
A fair coin is flipped and a fair spinner with three equal sections numbered 1, 2 and 3 is spun.
List the sample space. Find the probability of getting heads and an odd number.3 marks

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Written by the Exaim team, led by Shaun Daswani (Head of Upper Secondary, Improve ME Institute; MSc Financial Mathematics, Imperial College London; BSc, UCL) and Jason Daswani (operational lead, Improve ME Institute; LSE).