Question

Find the probability that the $13$th day of a randomly chosen month is a Friday.

• A. $\frac{1}{84}$
• B. $\frac{1}{7}$
• C. $\frac{1}{12}$
• D. $\frac{12}{365}$

Answer 1

Answer: (A)

$\frac{1}{84}$

Probability of chosen any month out of 12 month $=\frac{1}{12}$

And, 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.

So, its probability $=\frac{1}{7}$

Thus, required probability = $\frac{1}{12}\times \frac{1}{7}=\frac{1}{84}$

Hence, the probability that the 13$th$ day of a randomly chosen month is Friday = $\frac{1}{84}$