Clever horses
Logic
Level
3
You have 25 horses, and 5 tracks to race on.
Without any stopwatch, find the minimum races required to find the 3 fastest horses.
The answer is 7.
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1 solution
First divide the horses into 5 distinct groups & conduct 5 races among them.Choose top 3 horses of each group. (A1,A2,A3),(B1,B2,B3)(C1,C2,C3),(D1,D2,D3),(E1,E2,E3).[Speed of A1>A2>A3,same order for all other 4 groups.] Now conduct a race among A1,B1,C1,D1,E1.Let the top 3 be A1,B1,D1.So GROUP C & E are eliminated. Let A1>B1>D1.Again D1>D2>D3.So D2 &D3 are eliminated.A1>B1>B2>B3.So B3 is eliminated. Remaining contestants are A2,A3,B1,B2,D1.(A1 is not counted as it is the fastest one & will obviously qualify). Select top 2 among them and you are done conducting just 7 races.