Third Business Day

Assuming there is an equal chance that the given month begins with any of the seven days of the week, the answer is 3/7. That’s because Saturday and Sunday are non-working days, and therefore if the month starts with any of them, the third business day will still be Wednesday.

We note that 3/7 is actually an approximation of the actual answer, since the frequencies with which the days of the week appear as first in a given month, are close to but not equal to 1/7 each.