$A$ 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.

$4$ coins are tossed once. Find the probability of getting at least $1$ tail.

From a pack of cards,two are drawn,the first being replaced before the second is drawn. Find the probability that the first is a diamond and the second is a king.

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

In an entrance test,there are multiple-choice questions. There are four possible answers to each question,of which one is correct. The probability that a student knows the answer to a question is $90\%$. If he gets the correct answer to a question,then the probability that he was guessing is:

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