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How can you find 3 fastest horses among of 25 horses with 5 race tracks given to you to find out by race them up(in minimum races)?
I answered at 8 races. Divide 5 groups of five horses. Race one by one group and will get a fastest horse from every group.(5 races) Race between all 5 fastest horses of all group. (5+1 races). Race between all 5 second fastest horses of all group. (5+1+1 races). Race between all 5 third fastest horses of all group. (5+1+1+1 races).
You missed out the probability that all 3 horses might be of the same group
Divide 5 groups of 5 horses. Get top 3 in each group(5). You are left with 15. Then 3 more races in that group of 15 (5+3). You are left with 9. Then 2 more races in that group of 9(5+3+2). You are left with 6. Then 1 more race in that group of 6(5+3+2+1). You are left with 4. Then a last and race to decide best 3 of 4.(5+3+2+1+1). So, total comes to 12.
There was a tricky question on logical reasoning, which, if not encountered before, can be loopy. It goes like this: 3 men go to a hotel and pay the hotel manager a total of Rs. 30. (10 each) Later the manager realizes that the rent is Rs 25 and sends back Rs 5 via the bellboy. He then gives 1 each to the three men, which makes their net contribution Rs 9 each. The bellboy keeps the remaining Rs 2. So that makes it a total of Rs (3*9 + 2)= Rs 29. Where has the remaining Re 1 gone?