Mr. Prime always tell the truth when the day of the month is a prime number (i.e. the2 nd, 3rd, 5th, 7th,...), and lies on other days. Mr. Third always tell the truth on days that are multiplies of 3 (i.e. the 3rd, 6th, 9th, 12th,...), and lies on other days. On how many days in the month of April would both Mr. Prime and Mr. Third both say that they will lie the next day?

Guest Jun 19, 2022