Mathematics 0580 · IGCSE · Probability of combined events
Probability of combined events — practice question
Lucia has two fair spinners. Spinner A has 5 equal sections and is labelled 1, 2, 3, 4, 5. Spinner B has 9 equal sections and is labelled 3, 3, 4, 4, 4, 4, 5, 5, 5. Lucia spins both spinners and notes whether each result is a prime number.
(a(i))[2]
Fill in the tree diagram.
(a(ii)(a))[2]
Find the probability that both numbers are prime.
(a(ii)(b))[1]
Find the probability that the two numbers are not both prime.
(b)[1]
Lucia spins Spinner A 120 times. Find the expected number of times the spinner lands on a prime number.
(c)[3]
Lucia spins Spinner B twice. Find the probability that the two numbers it lands on add to 9 or more.
(d)[2]
Lucia keeps spinning Spinner B until it lands on a 4. Find an expression, in terms of $n$, for the probability that this occurs on the $n$th spin.
Worked solution & mark scheme
This 11-mark question has a full step-by-step worked solution and mark scheme. One marking point: “Correct probability \( \frac{2}{5} \) for spinner A” …