The number of permutations of 5 runners is 5 factorial=120, the number of orders in which they can end the race. We get this by looking at who comes first: any one of 5; that leaves 4 runners, one of 4 who comes second; that leaves 3 runners, one coming third; 2 runners, either one coming 4th; remaining runner coming last. Combine these: 5×4×3×2×1=120.