It was Monday on January 1, 2007. What was the day of the week on January 1, 2011?
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → Saturday
The weekday moves forward only by the odd days, the days left over after whole weeks. An ordinary year of 365 days is 52 weeks + 1 day, so it has 1 odd day; a leap year of 366 days has 2 odd days.
2007, an ordinary year: 1 odd day
2008, a leap year (divisible by 4), whose 29 February falls within the period: 2 odd days
2009 and 2010, ordinary years: 1 odd day each
Total from 1 January 2007 to 1 January 2011 \(=1+2+1+1=5\) odd days
Monday \(+\,5\) days \(=\) Saturday