The probability of a sure event is

$A$ box contains $15$ black and $20$ white balls. What is the probability that when $2$ balls are selected,at most one is white?

The word '$UNIVERSITY$' is arranged randomly. Then the probability that both '$I$'s do not come together is:

$A$ bag contains $30$ balls,of which $10$ are red,$5$ are blue,and $15$ are white. Find the probability of drawing a coloured ball at random.

One of the two events must occur. If the chance of one is $\frac{2}{3}$ of the other,then the odds in favour of the other are

Two cards are drawn one by one from a pack of cards. The probability of getting the first card as an ace and the second as a coloured card is (the first card is not replaced before drawing the second card).