Two cards are drawn at random one after the other with replacement from a pack of $52$ playing cards. Then the variance of the random variable of the number of spade cards among the drawn cards is

In a random experiment of throwing $5$ coins,the number of heads is defined as a random variable. The mean of the random variable is

Suppose that $90 \%$ of people are right-handed. What is the probability that at most $6$ of a random sample of $10$ people are right-handed?

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.

The probability of a bomb hitting a bridge is $1/2$ and two direct hits are needed to destroy it. Find the least number of bombs required so that the probability of the bridge being destroyed is greater than $0.9$.

For a binomial distribution with mean $6$ and variance $2$,the value of $P(X = 8)$ is