A bag contains $5$ black balls, $4$ white balls and $3$ red balls. If a ball is selected randomwise, the probability that it is a black or red ball is
$\frac{1}{3}$
$\frac{1}{4}$
$\frac{5}{{12}}$
$\frac{2}{3}$
The probability that a randomly chosen $5-digit$ number is made from exactly two digits is
Let $X$ be a set containing $n$ elements. If two subsets $A$ and $B$ of $X$ are picked at random, the probability that $A$ and $B$ have the same number of elements, is
The number lock of a suitcase has $4$ wheels, each labelled with ten digits i.e., from $0$ to $9 .$ The lock opens with a sequence of four digits with no repeats. What is the probability of a person getting the right sequence to open the suitcase?
There are $n$ letters and $n$ addressed envelops. The probability that each letter takes place in right envelop is
If four vertices of a regular octagon are chosen at random, then the probability that the quadrilateral formed by them is a rectangle is