Question

Ella was born early in the morning on a Friday. She got married on the 10,000th day of her life. What day of the week was it?

Answer 1

Notice that leap years do not matter in this problem because even if today is Tuesday and tomorrow is the 29th of February, tomorrow will still be Wednesday. (The same goes for if tomorrow is the 1st of March.) So, we can look for a pattern without worrying about tricks involving leap years or non-leap years. Notice that if today (the rst day of Ella's life) is Friday, on Ella's 8th day of life, it will be early Friday morning again. Similarly, on the 15th day of Ella's life, it will be Friday again. One way of saying this more easily is that on any day of Ella's life that is a multiple of 7, it is Thursday. So, because 9,996 is a multiple of 7, the 9,996th day of Ella's life is a Thursday. This makes the 10,000th day a Monday (since the 9,997th is Friday, 9,998th is Saturday and 9,999th is Sunday).

Answer 2

7n<10000

n<1428.5

10000-7(1428)=4

So she was married 4 days after friday, on a tuesday.