If the 19th of June 2001 is Tuesday, what will be the day of the week on the 21st of August 2009?
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → Friday
The weekday repeats every 7 days, so only the odd days, the days left over after whole weeks, move it forward. An ordinary year of 365 days is 52 weeks + 1 day, and a leap year (366 days) is 52 weeks + 2 days.
From 19 June 2001 to 19 June 2009 (8 years):
The 8 years include two 29 Februaries, in 2004 and 2008
Odd days: \(8\times1+2=10\), that is, 1 week + 3 days, so 3 odd days
19 June 2009 is Tuesday + 3 = Friday
From 19 June 2009 to 21 August 2009:
Rest of June: 30 − 19 = 11 days; July: 31 days; August: 21 days
Total \(11+31+21=63\) days = 9 whole weeks, so 0 odd days
21 August 2009 is the same weekday as 19 June 2009: Friday