(i)[3]
Find $\mu$.
(ii)[6]
Find the probability that, among $4$ straws chosen at random, fewer than $2$ have lengths between $21.5\,\text{cm}$ and $22.5\,\text{cm}$.
Mathematics 9709 · AS & A Level · Continuous random variables
Continuous random variables — practice question
The lengths, measured in centimetres, of drinking straws made in a factory follow a normal distribution with mean $\mu$ and variance $0.64$. It is stated that $10\%$ of the straws are less than $20\,\text{cm}$ long.