Puzzles are critical thinking problems that test a person's lateral thinking and problem-solving skills, similar to brain teasers. These types of puzzle questions are commonly used by interviewers to assess a potential employee's ability to solve complex problems using strategies and higher-order thinking to determine their fit for the company.

In this article, we will solve the puzzle â€˜fastest horsesâ€™.

Problem Statement

There are 25 horses, among which you need to find the top 3 fastest horses. You can conduct a race among at most 5 to determine their relative speed. Find out the minimum number of races that are required to determine the top 3 horses.

Note: You cannot find out the actual speed of the horse in a race at any point.

Hints

Find out the fastest horse and the group to which the fastest horse belongs. The group may contain 2nd and 3rd fastest horses.

Try to minimize races. Can you do it in 8 races? Then further try to lower the number.

Solution

First, make 5 groups, each group containing 5 horses, so a total of 25. After conducting 5 races, arrange the horses according to their ranks in a row. See the table below; the horses of each group are arranged according to their rank in a row.

Horses in column 5 are the fastest and in column 1 are the slowest; also in each row, horses are arranged according to their speed

Now conduct a race among column 5 horses. The horse that came first will be the fastest horse, and the horses which came second and third can be possible answers for 2nd and 3rd place. (Moreover shuffle the rows arrange, according to the horses that came 1st 2nd and 3rd, the row from which the fastest horse belongs will be on top, and the same is true for second and third).

Till now, there have been 6 races. And we have determined the fastest one. Now, which can be considered for the 2nd and 3rd positions?

For the second position,

The horse which came second in the 6th race can be a possible answer and,

The horse which came second from the group to which fastest horse(at position 1, the horse at row[1]col[5]) belongs.

These two horses will be just slower than the horse which came first and faster than all other horses. (Think over it)

Similarly for position 3, horses at position row[3]col[5], row[2]col[4] and row[1]col[3] are possibilities.

The horse may be the one that came third in the 6th race.

The one which came 3rd in the group to which the fastest horse belongs.

Also, a horse that is just slower than horses that are possibilities for 2nd position can be a solution, its horse row[2]col[4]

(Just think for a while).

Now we have 5 horses, and among these only, 2nd and 3rd fastest horses will be present. Conduct a race among them the horse which came first this time, will be second fastest horse and the one which came 2nd will be the third fastest.