Question 1
Tom tells the truth only on dates whose day of the month is divisible by 3 (for example, 3 January, 6 February, …); on all other dates he lies. Jerry tells the truth only on dates whose day of the month is divisible by 4 (for example, 4 January, 8 February, …); on all other dates he lies. In January 2021, on how many dates can both say, “I lied yesterday”?
