$A$ random variable $X \sim B(n, p)$. If the values of the mean and variance of $X$ are $18$ and $12$ respectively,then $n = $

An urn contains $25$ balls,of which $10$ balls bear a mark $'X'$ and the remaining $15$ bear a mark $'Y'$. $A$ ball is drawn at random from the urn,its mark is noted down,and it is replaced. If $6$ balls are drawn in this way,find the probability that at least one ball will bear the $'Y'$ mark.

$A$ coin is biased so that a head is twice as likely to occur as a tail. If the coin is tossed $3$ times,then the probability of getting two tails and one head is-

Find the probability distribution of the number of doublets in three throws of a pair of dice.

$A$ medicine for fever can cure $75\%$ of the people. Three people suffering from fever use this medicine. What is the probability that all three people are cured?

An urn contains $25$ balls of which $10$ balls bear a mark $'X'$ and the remaining $15$ bear a mark $'Y'$. $A$ ball is drawn at random from the urn,its mark is noted down and it is replaced. If $6$ balls are drawn in this way,find the probability that all will bear $'X'$ mark.