The digits are 1,2,3,4,5,6,7,8,9,and 0
The even ones are 0,2,4,6,8. The odd ones are 1,3,5,7,9
Let's try the even digit 0.
0×0 = 0. There is only one digit, so that can't be it.
Let's try the even digit 2.
2×2 = 4. There is only one digit, so that can't be it either.
Let's try the even digit 8.
8×8 = 64. Let's find the sum of the digits 6+4=10. No, 10 is not 9,
so it's not 8
I skipped the even digit 6, didn't I?
Let's try the even digit 6
6×6 = 36 and the sum of its digits is 3+6 or 9.
What do you know? That must be the answer, 6.
Now was that really too difficult for you to answer all by yourself?
Edwin
