Ok, there has been much heated debate at my house, at which i am greatly outnumbered, at the answers to these Qs:

1)You have an (countable) infinite number of balls, numbered 1,2,3,..... etc. and a box with infinite size.
At 1/1 minute to noon, you put the balls #1->10 in the box, and take ball #1 out.
At 1/2 minute to noon, you put the balls #11->20 in the box, and take ball #2 out.
At 1/3 minute to noon, you put the balls #21->30 in the box, and take ball #3 out.
You keep doing this, i.e at 1/n minutes to noon, you put in the box balls #10n-9 -> 10n and take out ball #n

The question is: How many balls are in the box at Noon?

N.B. This is thoetical, i.e. it takes no time to put it balls/take balls out of the box.

2)If you want some more to ponder, just think about what would happen if you took the #10n-9 ball out, instead of #n. How many balls wuold be in the box at noon then??