8-Digit Number Divisible by 9 Game

George and Frederik write out an 8-digit number, putting the numbers in order, starting with the highest digit. George starts. Can Frederik get the number to be divisible by 9?

Strategies in Games · Divisible by 9

Play as:

Your turn (George)

Sum: 0 mod 9: 0

Choose a digit

Controls

Why the second player wins

George and Frederik place digits left → right to make an 8-digit number (no leading 0).
Frederik replies so each pair (your digit + his digit) sums to 9.

If all 4 pairs sum to 9, the total digit-sum is 36 ⇒ divisible by 9. The second player can always force it.

Answer

Solution