Three numbers are chosen at random from numbers $1$ to $20$. The probability that they are consecutive is

If three cards are drawn randomly from a pack of $52$ playing cards,then the probability of getting exactly one spade card,exactly one king,and exactly one card having a prime number is

Three numbers are chosen at random without replacement from $\{1, 2, \ldots, 10\}$. The probability that the minimum of the chosen numbers is $3$ or their maximum is $7$ is:

Out of $21$ tickets marked with numbers from $1$ to $21$,three are drawn at random. The chance that the numbers on them are in $A.P.$ is

Two numbers $a$ and $b$ are chosen at random from the set of the first $30$ natural numbers. The probability that $a^2 - b^2$ is divisible by $3$ is

$A$ box contains $6$ black,$4$ red,$2$ white,and $3$ blue shirts. If $2$ shirts are picked at random,what is the probability that both are white or both are blue?