If 31 December 2009 was Thursday, then what was the day of the week on 25 December 2010?

Saturday

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 Dec 2009;

31 + 06 + 06 + 09 + 02 = 54

remainder of \(\frac{54}{7}\) = 05

Therefore, the code of 05 is Thursday

Similarly,

25 Dec 2010;

25 + 06 + 06 + 10 + 02 = 49

remainder of \(\frac{49}{7}\) = 0

Therefore, the code of 0 is Saturday