The probability that in a year of the $22^{nd}$ century chosen at random there will be $53$ Sundays is
$\frac{3}{{28}}$
$\frac{2}{{28}}$
$\frac{7}{{28}}$
$\frac{5}{{28}}$
Five horses are in a race. $Mr. \,A$ selects two of the horses at random and bets on them. The probability that $Mr.\, A$ selected the winning horse is
A determinant is chosen at random from the set of all determinants of order $2$ with elements $0$ or $1$ only. The probability that the determinant chosen is non-zero is
A fair coin is tossed four times, and a person win $\mathrm {Rs.}$ $1$ for each head and lose $\mathrm {Rs.}$ $1.50$ for each tail that turns up. From the sample space calculate how many different amounts of money you can have after four tosses and the probability of having each of these amounts.
A die is thrown. Describe the following events : $A$ : a number less than $7.$ Find the $A \cup B$.
There are $n$ letters and $n$ addressed envelopes. The probability that all the letters are not kept in the right envelope, is