GCSE · Basic probability
Probability of a single eventExam-style questions
Why a probability is a share of the whole — so it lives between 0 and 1, why P(A) = favourable ÷ total needs equally likely outcomes, and how the "it all adds to 1" rule drives complements, missing table entries and expected numbers.
13 questions · GCSE (Higher) level · mark scheme and worked solution on each · no sign-up to try
- 1A bag contains red counters, blue counters and green counters.
A counter is taken at random from the bag.
(a) Work out the probability that the counter is not green. (1 mark)
The counter is put back in the bag. This is repeated times.
(b) Work out an estimate for the number of times a green counter is taken. (2 marks)Level 2 · 3 marksTry it - 2A bag contains 5 red counters, 8 blue counters and 12 green counters.
A counter is taken at random from the bag.
(a) Write down the probability that the counter is blue.
(b) Work out the probability that the counter is not green.Level 2 · 3 marksTry it - 3A biased spinner can land on red, blue, green or yellow.
The table shows the probability that the spinner lands on each of three of these colours.
(a) Work out the probability that the spinner lands on yellow.Colour Red Blue Green Yellow Probability 0.2 0.35 0.15
(b) Work out the probability that the spinner does not land on blue.Level 2 · 3 marksTry it