to win $1 millon you must draw two cards whose sum is 9 from a stack of cards numberd 1 through 10 . after the first draw you replace the card and shuffle the stack again for the second draw. what is the chance that your two cards will have a sum of 9
could be
1,8
2,7
3,6
4,5
5,4
6,3
7,2
8,1
prob(1,8) = (1/10)(1/10) = 1/100
each of the remaining cases has the same prob
so prob = 8(1/100) = 8/100 = 2/25