How can you sort out your top 3 fastest horses?
You’ve recently bought 25 race horses from where you are to choose the fastest 3 for the upcoming competition.
Nearby your stable of horses there is a racing track with five lanes only, i.e., only five horses can run in the track at a time and each time you have to pay a good amount of money to the owner of the track for using it.
You only know that different horses has different running speed and the running speed of each horse remain constant whenever they run in a race. But you don’t have any idea about the individual running speed of any horse among the 25.
Now you can find out the fastest 3 horses by using the race track. You can use the track as many times as you want, but you have the constraint of time and money. Therefore, you have to use the track the minimum possible of times so that you will have to pay the minimum possible amount of money for the use of the track and will spend the minimum possible amount of time.
After each race the track owner provide you only the rank of each horse in the race, so you don't know how much time each horse took to complete the race.
Now the question is, what is the minimum number of times you have to use the race track so that you can find out the fastest 3 horses?