Question

In a given month, monday is the 21st day of the month. What day of the week was the 1st of the month?

Answer 1

1st, 8th, 15th, 22nd, 29th will be same days of the week in any month. i.e., same day repeats after every 7 days.

If 21st day of the month is monday, then 22nd day of the month will be tuesday. Since 22nd day of the month is tuesday, 1st of the month will also be tuesday.