Mathematics 9709 · AS & A Level · The Poisson distribution
The Poisson distribution — practice question
A triangular spinner has one red face, one blue face and one green face. The red face is weighted so that the chance of landing on red is four times the chance of landing on blue. The green face is weighted so that the spinner is three times as likely to stop on green as on blue.
(i)[1]
Show that the probability that the spinner lands on the blue side is $\frac{1}{8}$.
(ii)[3]
The spinner is spun $3$ times. Find the probability that it lands on a different coloured side each time.
(iii)[5]
The spinner is spun $136$ times. Use a suitable approximation to find the probability that it lands on the blue side fewer than $20$ times.
Worked solution & mark scheme
This 9-mark question has a full step-by-step worked solution and mark scheme. One marking point: “Correct probability equation $4p+p+3p=1$ giving $P(\text{blue})=\frac18$” …