(a)[1]
Find the value of $P(X = 8)$.
(b)[2]
Find the value of $P(X < 9)$.
(c)[3]
Find the probability that the second $3$ occurs before the $6$th throw.
Mathematics 9709 · AS & A Level · Discrete random variables
Discrete random variables — practice question
A fair six-sided dice whose faces are numbered $1, 2, 3, 4, 5, 6$ is rolled repeatedly until a $3$ appears. The number of rolls required is represented by the random variable $X$.
Worked solution & mark scheme
This 6-mark question has a full step-by-step worked solution and mark scheme. One marking point: “The correct probability is $P(X=8)=(\tfrac16)(\tfrac56)^7=0.0465$, or the equivalent fraction.” …
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