This question already has an answer here:

You've got 25 horses and you can host races in groups of 5. You don't have a stopwatch, obviously. Then what should be the minimum number of races that you should be conducting so as to ascertain the fastest 3 horses.


marked as duplicate by Jaap Scherphuis, Riley, ABcDexter, noedne, Deusovi May 26 '18 at 19:10

This question has been asked before and already has an answer. If those answers do not fully address your question, please ask a new question.