$A$ box contains $6$ nails and $10$ nuts. Half of the nails and half of the nuts are rusted. If one item is chosen at random,what is the probability that it is rusted or is a nail?

In a college,$40 \%$ of students attend the Mathematics class,$30 \%$ of students attend the Physics class,and $20 \%$ of students attend both classes. If a student is chosen at random from the college,what is the probability that the chosen student attends only one class?

$A$ coin is tossed $3$ times. The probability of getting exactly two heads is

$A$ six-faced unbiased die is thrown twice and the sum of the numbers appearing on the upper face is observed to be $7$. The probability that the number $3$ has appeared at least once is:

$A$ card is selected from a pack of $52$ cards. Calculate the probability that the card is an ace.

$A$ box contains $4$ white pens and $2$ black pens. Another box contains $3$ white pens and $5$ black pens. If one pen is selected from each box,then the probability that both the pens are white is equal to