What is the probability that the sum of two numbers chosen at random from $40$ consecutive natural numbers is odd?

$A$ bag contains $4$ red,$5$ white,and $6$ black balls. If three balls are drawn at random,what is the probability that they are of different colors?

Two digits are selected randomly from the set $\{1, 2, 3, 4, 5, 6, 7, 8\}$ without replacement one by one. The probability that the minimum of the two digits is less than $5$ is

Three dice are rolled. If the probability of getting different numbers on the three dice is $\frac{p}{q}$,where $p$ and $q$ are co-prime,then $q-p$ is equal to

$A$ box contains coupons labelled $1, 2, \ldots, 100$. Five coupons are picked at random one after another without replacement. Let the numbers on the coupons be $x_1, x_2, \ldots, x_5$. What is the probability that $x_1 > x_2 > x_3$ and $x_3 < x_4 < x_5$?

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