The probability of a sure event is .

For any event $E, P\left(E\right)+P\left(\mathrm{not} E\right)=$_____.

The sum of probabilities of all the outcomes of an experiment is _____.

Two coins are tossed simultaneously. Find the probability of getting at least $1$ head

If the answer is of the form $\frac{a}{b}$, then what is the value of $b$? 

A die is thrown once. Find the probability of getting an even number

A die is thrown once. Find the probability of getting a number less than $5$