The probability of getting two heads in the experiment of tossing an unbiased coin twice is .........

In a musical chair game,the person playing the music has been advised to stop playing the music at any time within $2 \, \text{minutes}$ after she starts playing. What is the probability that the music will stop within the first half-minute after starting?

If an event cannot occur,then its probability is

$A$ balanced die is thrown once. Find the probability of getting a prime number.

There are $5$ white,$7$ red,$4$ black,and $2$ blue identical balls in a box. One ball is selected at random from the box. Find the probability that the selected ball is either white or blue.

The probability of a non-leap year having $53$ Fridays is $\ldots \ldots \ldots$