Percent on 100 tries?

Question

If i know that something happens 50% In 1 try.

What is percent of Something to Happen at least once in 100 tries?

My friend told me that chances are 50% but i dont understand how that is possible?

could you explain with more details please

Answer 1

Let us consider tossing a fair coin (equivalent to your problem). Now, the probability of getting no heads in 100 tosses is

$$P(\text{No Heads}) = \frac{1}{2^{100}}$$

Now, any other case other than this case has at least one head. Hence, since the total probability of all events occurring is one, we have

$$P(\text{At Least One Head}) = 1 - \frac{1}{2^{100}}$$

This is much much bigger than 50%