3 An experiment consists of throwing a biased die 30 times and noting the number of 4 s obtained. This experiment was repeated many times and the average number of 4 s obtained in 30 throws was found to be 6.21.
- Estimate the probability of throwing a 4.
..................................................................................................................................... .
\section*{Hence} - find the variance of the number of 4 s obtained in 30 throws,
- find the probability that in 15 throws the number of 4 s obtained is 2 or more.