to win 1 million dollars,you must draw two cards whose sum is 9 , from a stack of cards numbered 1 though 10 .After the first draw, you replace the card and shuffle the stack again for for the second draw. Wat is the chance your two cards will have a sum of nine?

Answer 1

Here are the possible ways to sum 9 with 2 cards.

8 + 1
7 + 2
6 + 3
5 + 4
1 + 8
2 + 7
3 + 6
4 + 5

Each pair has the probability of (1/10)^2. The probability of either-or events is determined by the sum of the individual events.

I hope this helps.