If you don't believe that this works, try it!
Here is a table showing the possible coins that you could select for group one, and the resulting number of tails in group two:|
Group One (10 coins) If you select: |
Group Two (90 coins) | |
|---|---|---|
| 0 Tails | 10 Heads | 10 Tails |
| 1 Tail | 9 Heads | 9 Tails |
| 2 Tails | 8 Heads | 8 Tails |
| 3 Tails | 7 Heads | 7 Tails |
| 4 Tails | 6 Heads | 6 Tails |
| 5 Tails | 5 Heads | 5 Tails |
| 6 Tails | 4 Heads | 4 Tails |
| 7 Tails | 3 Heads | 3 Tails |
| 8 Tails | 2 Heads | 2 Tails |
| 9 Tails | 1 Heads | 1 Tail |
| 10 Tails | 0 Heads | 0 Tails |