In a single throw of $2$ dice,what is the probability of getting a total of $7$?

In a box,there are $2$ red,$3$ black,and $4$ white balls. If three balls are drawn together,what is the probability that the balls drawn are of the same colour?

Let $0 < P(A) < 1$,$0 < P(B) < 1$ and $P(A \cup B) = P(A) + P(B) - P(A)P(B).$ Then

Two dice are tossed. The probability that the total score is a prime number is

$A$ and $B$ throw a coin alternately till $1$ of them gets a head and wins the game. If $A$ starts the game,find the probability of $A$ winning.

An urn contains $25$ balls numbered $1$ to $25$. Suppose an odd number is considered a 'success'. $2$ balls are drawn from the urn with replacement. Find the probability of getting at least one success.