9709 P53 - Nov 2020 - Q6
2892
Three coins A, B and C are each thrown once.
- Coins A and B are each biased so that the probability of obtaining a head is \(\frac{2}{3}\).
- Coin C is biased so that the probability of obtaining a head is \(\frac{4}{5}\).
(a) Show that the probability of obtaining exactly 2 heads and 1 tail is \(\frac{4}{9}\).
The random variable \(X\) is the number of heads obtained when the three coins are thrown.
(b) Draw up the probability distribution table for \(X\).
(c) Given that \(\text{E}(X) = \frac{32}{15}\), find \(\text{Var}(X)\).
