Question

The probability that the $13th$ day of a randomly chosen month is a Friday, is

• A. $\frac{1}{12}$
• B. $\frac{1}{7}$
• C. $\frac{1}{84}$
• D. None of these

Answer 1

The correct option is C $\frac{1}{84}$

Any month out of $12$ months, can be chosen with probability $=\frac{1}{12}$.
There are $7$ possible ways in which the month can start and it will be a Friday on $13th$ day if the first day of the month is Sunday,
Its probability $=\frac{1}{7}$
Hence the required probability $=\frac{1}{12}\times \frac{1}{7}=\frac{1}{84}$