Mathematics 9709 · AS & A Level · Linear combinations of random variables
Linear combinations of random variables — practice question
A spinner has $5$ equal sectors, labelled $1$, $2$, $3$, $4$ and $5$. The number on the sector where it stops is taken as the score. This score is represented by the random variable $X$, and its probability distribution is listed in the table: $P(X=1)=0.3$, $P(X=2)=0.15$, $P(X=3)=3p$, $P(X=4)=2p$, $P(X=5)=0.05$. There is also a second spinner with $3$ sectors, labelled $1$, $2$ and $3$. The score from this spinner is represented by the random variable $Y$. It is known that $P(Y=1)=0.3$, $P(Y=2)=0.5$ and $P(Y=3)=0.2$.
(i)[1]
Find the value of $p$.
(ii(a))[3]
Find the probability that, when both spinners are spun together, the sum of the scores is $4$.
(ii(b))[3]
Find the probability that, when both spinners are spun together, the product of the scores is less than $8$.
Worked solution & mark scheme
This 7-mark question has a full step-by-step worked solution and mark scheme. One marking point: “The correct value is $p=0.1$” …