Why do the opposing numbers on a standard round clock add up to 12?

Question

If you look at a clock and use 12 and 6 to divide it in half, why do the opposite numbers add up to 12...... 11 and 1, 10 and 2, 9 and 3, 8 and 4, 7 and 5>

Answer 1

Because if one number is n in the clockwise direction, its opposing number will be n away from 12: so n + (12-n)=n always.

Answer 2

12 + 6 is 18.