There are $n$ letters and $n$ addressed envelopes. The probability that all the letters are not kept in the right envelope,is

Find the probability that a two-digit number formed by the digits $1, 2, 3, 4, 5$ is divisible by $4$ (repetition of digits is allowed).

In a class of $25$ students with roll numbers $1$ to $25,$ a student is picked up at random to answer a question. Find the probability that the roll number of the selected student is either a multiple of $5$ or $7$.

$A$ determinant is chosen at random from the set of all determinants of order $2$ with elements $0$ or $1$ only. The probability that the determinant chosen is non-zero is

The probabilities that a student will receive an $A$, $B$, $C$, or $D$ grade are $0.30$, $0.38$, $0.22$, and $0.01$ respectively. What is the probability that the student will receive at least $B$ grade?

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 no success.