IBM Ponder This #015 · July 1999

Ten bowling pins are arranged in a triangle and labelled with the distinct integers $0,1,\dots ,9$. Whenever two pins are side by side, the sum of their labels, reduced modulo $10$, equals the label of the pin in front of and between them.

How are the pins labelled?

Solution

Best opened after a real attempt

Solution

To be added.