You have 5 chances in 100 to win the first prize.

Then that winning ticket is discarded, so you are left with 4 chances in 99 to win the 2nd prizeifyou won the first prize.

You have 95 chances in 100 not to win the 1st prize and 94 chances in 99 not to win the 2ndifyou didn't win the first.

The probability of winning at least one prize is the probability of winning no prize subtracted from 1.

Maybe you could try calculating those