Question

Calculate the probability of needing at least 5 tosses of an unbiased coin to land a head.

Answer 1

0.03125

Explanation:

If we have a fair coin the probability of landing a head is 50%.

We can think the question as what is the probability of landing four tails and then a head. That is we needed at least 5 tries to get a head.

`Prob \{ T,T,T,T,H\}`

Since this events are independent we can write it as

`Prob \{ T\} * Prob \{ T\} * Prob \{ T\} * Prob \{ T\} * Prob \{ H\} =.5^5= 0.03125`