The probability of at least one of the events $A$ and $B$ occurring is $0.6$. If the probability of both $A$ and $B$ occurring simultaneously is $0.3$,then $P(A') + P(B') = \dots$

One card is drawn from a well-shuffled deck of $52$ cards. If each outcome is equally likely,calculate the probability that the card will be a diamond.

From a pack of $52$ cards,one card is drawn at random. The probability that it is either a king or a queen is:

The probability of choosing randomly a number $c$ from the set $\{1, 2, 3, \ldots, 9\}$ such that the quadratic equation $x^2 + 4x + c = 0$ has real roots is

What is the probability that when one die is thrown,the number appearing on top is even?

The probability of solving a problem by three persons $A, B$ and $C$ independently is $\frac{1}{2}, \frac{1}{4}$ and $\frac{1}{3}$ respectively. Then the probability that the problem is solved by exactly two of them is