(a)[3]
Using $\text{E}(X) = 1.1$, determine the values of $p$ and $r$.
(b)[2]
Calculate the numerical value of $\mathrm{Var}(X)$.
Mathematics 9709 · AS & A Level · Discrete random variables
Discrete random variables — practice question
In a throwing competition, a competitor gets three attempts to throw a ball as far as possible. The random variable $X$ represents how many throws go beyond $30$ metres. The probability distribution table for $X$ is given below.
Worked solution & mark scheme
This 5-mark question has a full step-by-step worked solution and mark scheme. One marking point: “Total probability: $p+r+0.55=1$ (or, equivalently, $p+r=0.45$).” …
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