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

From a collection of eight cards numbered $1$ to $8$,if two cards are drawn at random,one after the other with replacement,then the probability that the product of the numbers that appear on the cards is a perfect square is

Let $X = \{(x, y) \in \mathbb{Z} \times \mathbb{Z} : \frac{x^2}{8} + \frac{y^2}{20} < 1 \text{ and } y^2 < 5x\}$. Three distinct points $P, Q,$ and $R$ are randomly chosen from $X$. Then the probability that $P, Q,$ and $R$ form a triangle whose area is a positive integer is

$A$ bag contains $a$ white and $b$ black balls. Two players $A$ and $B$ alternately draw a ball from the bag,replacing the ball each time after the draw,until one of them draws a white ball and wins the game. $A$ begins the game. If the probability of $A$ winning the game is three times that of $B$,then the ratio $a : b$ is

In a game of cards,what is the probability that a specific player holds all $4$ kings in a hand of $13$ cards?

Two cards are drawn at random from a standard pack of $52$ cards. The probability that the draw consists of exactly one face card and exactly one ace card is