Label the nine people by the letters A through to I. The solution, which involves four days of walking, is to arrange them into the following triples:
| Day 1: | ABC | DEF | GHI |
| Day 2: | ADG | BEH | CFI |
| Day 3: | AEI | BFG | CDH |
| Day 4: | AFH | BDI | CEG |
Plus.Maths.org
Label the nine people by the letters A through to I. The solution, which involves four days of walking, is to arrange them into the following triples:
| Day 1: | ABC | DEF | GHI |
| Day 2: | ADG | BEH | CFI |
| Day 3: | AEI | BFG | CDH |
| Day 4: | AFH | BDI | CEG |