As the area gets larger, so do the number of coordinates in the area exponentially. So, when for a 10*10 you needed 100 tickets, 30*30 area is already 900 possible coordinates! And as the maximum number of tickets you could buy for one game was 150, you will not be able to be a “100% winner” even if you were to able to narrow the area down to 30*30 pixels.
But, completely hypothetically once again: If you are able to play the 150 tickets in a 30×30 area (and would place the tickets at random in this area), there would be a 16.67% chance of you getting the exact coordinate right. However, usually the winners of the competition don’t get the exact coordinate right, so most of the time being close enough is enough to win. (And you don’t need to be ‘bang on’ with the coordinate!)