If November 1, 2019 was Friday, then what was the day on December 2, 2011?
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → Friday
The weekday repeats every 7 days, so only the odd days, the days left over after whole weeks, move it. A year of 365 days has 1 odd day and a year of 366 days has 2. The quickest route is to find the day of 2 December 2019 first and then go back eight years to 2 December 2011.
From 1 November 2019 to 2 December 2019:
November has 30 days, so 1 December 2019 is 30 days later and 2 December 2019 is 31 days later
\(31=4\times7+3\), so 3 odd days: Friday + 3 = Monday, 2 December 2019
From 2 December 2011 to 2 December 2019 (eight years):
The period contains two 29 Februaries, in 2012 and 2016; the other six years have 365 days
Odd days: \(6\times1+2\times2=10\), that is \(7+3\), so 3 odd days
2 December 2019 is 3 days of the week ahead of 2 December 2011, so 2 December 2011 is Monday − 3 = Friday