# How to derive the chances of getting the Jackpot in NY Mega Millions with the given answer?

You choose 5 numbers from within the set {$1,2,...,75$}, in $75C5=17259390$ ("75 choose 5") ways. Then you multiply by 15 , because you can choose the additional ball in 15 ways. Then you have $17259390)(15)=258890850$