Horse Race

Horse race



Puzzle :

            The puzzle is there are 25 horses among which you need to find out the fastest 3 horses. You can conduct race among at most 5 horses to find out their relative speed. At no point you can find out the actual speed of the horse in a race. Find out how many races are required to get the top 3 horses. The answer for this puzzle is given below.

Answer :

         Seven.
The first 5 to find the 3 fastest in each group and the sixth with the winners of each group.Now we know the fastest horse.
The second fastest horse must either be the second fastest in the sixth race or the second fastest horse in the final winners first race.
In the first case, the third fastest horse can either be the third fastest horse in the sixth race or the second fastest horse in either the fastest or second fastest horses first race.
Otherwise the third fastest horse could either be the second fastest horse in the sixth race or the third fastest horse in the final winners first race.
This makes for a total of five horses for the seventh, and final, race.



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