Three squares of a chessboard are selected at random. The probability of selecting two squares of one colour and the other of a different colour is equal to

$A$ bag contains $6$ white and $4$ black balls. Two balls are drawn at random. The probability that they are of the same colour is

Two persons $A$ and $B$ take turns in throwing a pair of dice. The first person to throw a sum of $9$ with both dice will be awarded the prize. If $A$ throws first,then the probability that $B$ wins the game is

If two cards are drawn at random simultaneously from a well-shuffled pack of $52$ playing cards,then the probability of getting a card having a composite number and a card having a number which is a multiple of $3$ is

From a month of $31$ days,$3$ different dates are selected at random. If the probability that these dates are in an increasing $A$.$P$. is equal to $\frac{a}{b}$,where $a, b \in N$ and $\text{gcd}(a, b) = 1$,then $a + b$ is equal to ————

If three dice are thrown simultaneously,then the probability of getting a score of $7$ is