Probability of Head in coin flip when coin is flipped two times Probability of getting a head in coin flip is $1/2$. 
If the coin is flipped two times what is the probability of getting a head in either of those attempts?
I think both the coin flips are mutually exclusive events, so the probability would be getting head in attempt $1$ or attempt $2$ which is:
$$P(\text{attempt $1$}) + P(\text{attempt $2$}) =  1/2 + 1/2 = 1$$
$100\%$ probability sounds wrong? What am I doing wrong. If I apply the same logic then probability of getting at least $1$ head in $3$ attempt will be $1/2+1/2+1/2 = 3/2 = 1.5$ which I know for sure is wrong. What do I have mixed up?

Let $A$ be the event of getting a tail in both tosses, then $A'$ be the event of getting a head in either tosses. So $P(A') = 1 - P(A) = 1 - 0.5*0.5 = 0.75$
