Logic Puzzles

Look at the shapes of the digits. How many closed loops (holes) does each digit contain?

The rule is to count the number of closed loops in the digits.

• 9 9 9 9: each 9 has one loop → 4 loops.
• 8 8 8 8: each 8 has two loops → 8 loops.
• 1 8 1 6: 8 has two loops, 6 has one → 3 loops.
• 1 2 1 2: digits 1 and 2 have no loops → 0 loops.

For 1 9 1 9, each 9 contributes one loop and the 1s contribute none, giving 2 loops in total.

Therefore the missing digit is 2.