Answer:
1/1000 = 0.001
Explanation:
Out of the 1000 tickets only one will be chosen. And since you only bought one ticket you would get a 1/1000 chance to get chosen. If you turn 1/1000 into a decimal you get 0.001 or 0.1%. Say if you bought 2 tickets you would get a 2/1000 chance which would be a 0.2% chance and so on.