The probability of an event can be calculated from the odds against that event. The formula for converting odds against to probability is:
Probability = 1 / (1 + odds against)
So in this case, the odds against winning $1.00 in the lottery are 19 to 1, and the probability of winning can be calculated as follows:
Probability = 1 / (1 + 19) = 1 / 20 = 0.05
So the probability of winning $1.00 in the lottery is 0.05, or 5%.