Solution to the Problem:
The missing number is 12.The number in each circle is determined by adding up the digits of all numbers pointing to that circle.
For example, 27 = 7 + 2 + 9 + 9
18 = 2 + 7 + 4 + 5
so the missing number ? = 2 + 1 + 3 + 6 = 12
Correctly solved by:
| 1. Ivy Joseph | Pune, Maharashtra, India |
| 2. Colin (Yowie) Bowey | Beechworth, Victoria, Australia |
| 3. Veena Mg | Bangalore, Karnataka, India |
| 4. Katherine Grossman |
Redlands Middle School, Grand Junction, Colorado |