If 31 August 2000 was Friday, then what was the day of the week on 31 August 2009?

Tuesday

Using Code Method :-

\(\frac{Date+Month code+Year code+Last 2 digits of yr+Leap yrs till given yr}{7}\)

( Note: Remainder of the above sum will be the code of week day }

31 Aug 2000;

31 + 03 + 06 + 0 + 0 = 40

remainder of \(\frac{40}{7}\) = 05

Therefore, the code of 05 is Thursday + 01 = ( Friday )

Similarly,

31 Aug 2009;

31 + 03 + 06 + 09 + 02 = 51

remainder of \(\frac{51}{7}\) = 02

Therefore, the code of 02 is Monday + 01 ( Tuesday )