If a number is selected at random from one-digit natural numbers,the probability of that number being a multiple of $3$ is ..... .

When we toss a coin,there are two possible outcomes - Head or Tail. Therefore,the probability of each outcome is $\frac{1}{2}$. Justify your answer.

$A$ carton of $24$ bulbs contains $6$ defective bulbs. One bulb is drawn at random. What is the probability that the bulb is not defective? If the bulb selected is defective and it is not replaced, and a second bulb is selected at random from the rest, what is the probability that the second bulb is defective?

Two balanced dice are rolled simultaneously. Then,the probability that the sum of numbers on the dice is $13$ is ..............

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

There are chits numbered $1$ to $20$ in a box. One chit is drawn at random. Find the probability that the number on the chit is a prime number.