Probability Question(s)

(I knew I shouldive stayed awake in statistics class)

Let's say your school was holding a lottery, and the winner would recieve $100. The chances of winning the lottery with 1 ticket is only 1/50, BUT: What are the odds of winning if you use like 20 tickets?

This is the OR principle.  Your first ticket could win OR your second could win OR your third, etc.  You add the separate probabilities with OR.  With fractions, the numerator is the number of tickets you bought, and the denominator is the total number of tickets in play.

If you are using lottery numbers, then the numerator is the total number of unique combinations you played and the denominator is the total number of number combinations possible according to how the lottery is set up.  For example if the lottery has you choose 6 numbers out of 49, then there are 49C6 combinations (look up the formula or use a scientific calculator with a nCr button) which is nearly 14 million.