Kelly was watching her favorite Winter Olympic event – the four-man bobsled. On each team a driver sits in front, followed by two teammates and the brakeman in the back.
The numbers 1 through 20 were assigned to the 20 athletes. The drivers wore numbers 1, 2, 3, 4, and 5.
Before the race Kelly studied the teams. Drivers 2, 3, and 4 were riding with brakemen 18, 15, and 20 respectively in three of the sleds. In another sled were 6 and 12, and in the remaining sled were 10 and 17.
Suddenly Kelly realized that if you added up the four numbers on each team, all five sums were the same!