Horses, Horses
How many races must you conduct, in order to find the fastest 3 horses in a group of 25?
I'm away from the press room this weekend, and I've just received the call no publisher wants to hear. The hotshot freelancer we hired for this week's feature was arrested in a case of mistaken identity / political intrigue / intra-magical infighting. His situation seems to be resolving on its own—the guilty twin was uncovered, the corrupt Student Body President wound up stapled to a bulletin board, and the hat-rabbits buried their tiny little hatchets—but that still leaves me without a front page. I tried calling Arnie Tackleman, hoping he could write a quick outdoor piece. No answer, all afternoon. He's up a creek somewhere, I presume. I tried Vera Maraschino, too, and, got no answer from her, either. Probably at some chic boutique, with her ringer off.
Thus, I must fall upon the newspaper's last, most reliable refuge, the Puzzle Page. I'm no Will Shortz, as you know, just a humble tycoon. I'm not equipped to make up puzzles on the spot, but I'm reasonably good at borrowing.
So, a logic puzzle for you—
You are a horse-race fixer for an upstanding "family organization." Your employer, Johnny “Mud Dauber” Daubins, has commanded you to find the fastest three horses in his twenty-five-horse stable. To do this, you must use the narrow racetrack on the Daubins Family estate, which can field only five horses at a time. Though your employer fully plans to exploit his horses, he wants to keep them strong and until then, so you must accomplish your task efficiently, running only the minimum necessary races. Run more races than you need, and you’ll definitely wake up with a...Godfather problem. Lastly, because Daubins is a paranoid maniac, you're not allowed to wear a watch (or a phone, or a kitchen timer—I see you, loophole guy.)
To sum up: How many races must you conduct, in order to find the fastest 3 horses in a group of 25? Fine print: Five horses per race, there's only one track, and you can't record the track times. What strategy requires the fewest races?
F.A.Q
What if I don’t like logic puzzles?
It's a filler article, friend. See you next week. Go in peace.
Can you definitively say one horse is faster than another, based on just one race?
With normal horses, no, but these are Extrathoroughbreds, genetically-engineered for extreme consistency. All races between the same two horses will yield the same winner, and render the same loser.
Won't a horse perform worse, if it's tired?
You can rest the horses between each race. It's the number of races Mr. Daubins wants to limit, not the number of days. But do make sure he gets his answer before the Belmont Stakes, because of reasons.
What if I already know this puzzle?
Your choice: Find a proof for P versus NP, or treat yourself to a nice, hot bath.
Should I send in my answer? Is there a prize?
You don't need to send your answer, though you certainly may. If you're proud of your solution, or you want someone to witness your brilliance, by all means, send it my way. (Reply to this email, or hit up Noré, our client service manager, noreply@casualobserver.co) There's no prize, though. Unless I change my mind and decide there's a prize.
Best of luck! I'll print the answer next Sunday.
(The solution to this puzzle has now appeared. When you're ready, see it here.)
