$4$ coins are tossed once. Find the probability of $4$ tails.

$A$ bag contains $4$ white,$5$ black,and $6$ red balls. If a ball is drawn at random,what is the probability that the drawn ball is either white or red?

$A$ bag $A$ contains $2$ white and $3$ red balls and bag $B$ contains $4$ white and $5$ red balls. One ball is drawn at random from a randomly chosen bag and is found to be red. The probability that it was drawn from bag $B$ is:

While dialing a telephone number,an old man forgets the last two digits,remembering only that they are different. If he dials the last two digits at random,what is the probability that the number is dialed correctly?

An urn contains $25$ balls numbered $1$ to $25$. Suppose an odd number is considered a 'success'. $2$ balls are drawn from the urn with replacement. Find the probability of getting $3$ successes.

$A$ bag contains $3$ red and $5$ black balls and a second bag contains $6$ red and $4$ black balls. $A$ ball is drawn from each bag. The probability that one is red and the other is black,is