DAY 230

SQUARE DANCE
Credit: GAMES Magazine - Oct/Nov 1987
Guney Mentes

Sally invited 17 guests to her party. She assigned each guest a number from 2 to 18, keeping 1 for herself. When everyone was dancing, Sally noticed that the sum of each couple's numbers was a perfect square. What was the number of Sally's partner?

HINT:
Start with guest 18.

Answer:

Sally's partner was guest 15. The pairings were 18-7, 17-8, 16-9, 15-1, 14-2, 13-3, 12-4, 11-5, and 10-6.