How do you calculate probability?

Divide the number of favourable outcomes by the total number of possible outcomes, then simplify. It can be written as a fraction, a decimal, or a percent.

How do you find the probability of two independent events both happening?

Multiply their individual probabilities: P(A and B) = P(A) × P(B).

Can a probability be more than 1?

No, probability ranges from 0 (impossible) to 1 (certain).

How do you find P(A or B)?

If A and B can't both happen (mutually exclusive), add their probabilities. If they can overlap, add them and then subtract P(A and B) so the overlap isn't counted twice.

What is conditional probability?

The probability of an event given that another event has already happened — e.g. the probability a second card is red, given the first one drawn (and not replaced) was also red.

Probability · Grades 6–12

Probability Worksheets

The ones you want over all the ones there are. Probability worksheets covering single events with marbles and dice (as a fraction, decimal, or percent) and, from Grade 7, two independent events together. Grade 12 adds OR-events, conditional probability, and binomial probability.

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What it is

Probability measures how likely an event is, from 0 (impossible) to 1 (certain), as favourable outcomes over total outcomes.

Why it matters

Probability underlies statistics, games, risk, and decision-making, a key numeracy skill for everyday life.

How to do it

Count the favourable outcomes.
Count the total possible outcomes.
Write favourable ÷ total and simplify the fraction.

Examples by level

BeginnerA bag has 1 red and 1 blue marbles. P(blue) =1/2
IntermediateP(flipping heads on a coin AND rolling a 3 on a die) =1/12
AdvancedRolling a fair die, P(a 3) =16.7%

Examples are generated by the same engine as the worksheets, so they're always mathematically correct. Built to avoid repeats, not reshuffle the same handful of questions.

Common mistakes

Using the favourable count as the total.
Forgetting to simplify the fraction.
Giving an answer above 1.
Adding two independent events' probabilities instead of multiplying them.
Adding P(A) and P(B) for P(A or B) without checking whether the events overlap — an overlap must be subtracted once.

Tips

Probability is always between 0 and 1.
Simplify the fraction like any other.
For two independent events, P(A and B) = P(A) × P(B) — multiply, don't add.

For parents

Probability is 'the ones you want' over 'all the ones there are', then simplify.

For teachers

Anchor the 0-to-1 scale (impossible → certain) before computing fractions.

Key vocabulary

outcome: a possible result
event: the outcome(s) you want
probability: favourable ÷ total
independent events: events where one doesn't affect the other's probability; their combined probability is the product of each

Frequently asked questions

How do you calculate probability?: Divide the number of favourable outcomes by the total number of possible outcomes, then simplify. It can be written as a fraction, a decimal, or a percent.
How do you find the probability of two independent events both happening?: Multiply their individual probabilities: P(A and B) = P(A) × P(B).
Can a probability be more than 1?: No, probability ranges from 0 (impossible) to 1 (certain).
How do you find P(A or B)?: If A and B can't both happen (mutually exclusive), add their probabilities. If they can overlap, add them and then subtract P(A and B) so the overlap isn't counted twice.
What is conditional probability?: The probability of an event given that another event has already happened — e.g. the probability a second card is red, given the first one drawn (and not replaced) was also red.

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