If $P(\overline{B}) = 0.81$,then $P(B) = \ldots$

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 red or black. (in $/18$)

There are boards numbered $1$ to $50$ in a box. One board is selected at random. Find the probability that the number on the board is a multiple of $10$. (in $/10$)

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

One ticket is drawn at random from a bag containing tickets numbered $1$ to $40$. The probability that the selected ticket has a number which is a multiple of $5$ is

Two unbiased dice are thrown once. Write all the possible outcomes of this experiment. What is the probability that the sum of numbers on two dice is smaller than $5$?