Question

If a fair coin is tossed $10$ times, find the probability of appearing exactly four tails.

Answer 1

Out of the ten options, four of them have to be tails.

The number of ways of choosing these four places out of ten is given by ${}^{10}{C}_4$

Now, the probability of occurrence of tails and heads for a fair coin is $\frac{1}{2}$

$\therefore$ the final probability can be written as ${}^{10}{C}_4\times \frac{1}{2^{10}}$