I believe its 1/720. There are 10 possible numbers. You need to match all three. The odds of the first match is 1/10. However after that they will draw a new number if the first number comes up again. So for the second drawing there are basically only 9 possibilities. So the odds of hitting the second number is 1/9. Similarly for the third it is 1/8. So your chances of hitting all three are 1/10 * 1/9 * 1/8 = 1/720.