I'm sorry but that is not how the numbers work.....
It is a 10 in 120 chance, followed by a 10 in 119 chance, followed by a 10 in 118 chance....
Chance of winning is then 1 - chance of failing all 3 pulls with 10 tickets
or
1 - [ ( 110 / 120) * (109 / 119) * (108/118) ] which still equals about a 23% chance.... but your reason is wrong D:
.... I hope this is not how they are teaching math now a days because while this can be used for approximation, it is still wrong :C
Is this a Common Core thing? Because it seems like one of the shortcuts that they try to teach in common core that is making us in higher education cry