In a single throw of two dice,the probability of obtaining an odd number as the sum is

There are $4$ envelopes with addresses and $4$ corresponding letters. The probability that no letter goes into its correct envelope is:

The probability of an event $A$ occurring is $0.5$ and that of $B$ is $0.3$. If $A$ and $B$ are mutually exclusive events,find the probability that neither $A$ nor $B$ occurs.

$A$ bag contains $4$ white balls and $2$ black balls. Another bag contains $3$ white balls and $5$ black balls. If one ball is drawn from each bag,then the probability that both the balls are black,is

An integer is chosen at random and squared. The probability that the last digit of the square is $1$ or $5$ is

$A$ problem of mathematics is given to three students whose chances of solving the problem are $\frac{1}{3}$,$\frac{1}{4}$,and $\frac{1}{5}$ respectively. The probability that the question will be solved is