1 Every time a spinner is spun, the probability that it shows the number 4 is 0.2 , independently of all other spins.
- A pupil spins the spinner repeatedly until it shows the number 4 .
Find the mean of the number of spins required.
- Calculate the probability that the number of spins required is between 3 and 10 inclusive.
- Each pupil in a class of 30 spins the spinner until it shows the number 4 . Out of the 30 pupils, the number of pupils who require at least 10 spins is denoted by \(X\).
Determine the variance of \(X\).