Question { State Bank Of India SBI, 39102 }

What is the minimum number of races required to pick the
best three horses from 25 horses if each race has maximum of
5 horses?

Answer

It is seven.....
It is already given by some one .....
But I will try to make it more clear.....

First conduct 5 races with the given 25 horses......
so we will get :
Races : 1 2 3 4 5
First : 1 1 1 1 1
Second : 2 2 2 2 2
Third : 3 3 3 3 3
Fourth : 4 4 4 4 4
Fifth : 5 5 5 5 5

So we are sure that the fastest would be from the horses
which stood first in each race........
that is from First: 1 1 1 1 1

So next we must conduct the race among all the horses which
stood first in each race,i.e. race no 6:

Than we will get the fastest......

Next we have to get the second fastest and third fastest..

Now we have the options like this:

Now the second might be the second from the 6th race or the
second from the earlier conducted race where the fastest
was the first.....

Third might be the third from the 6th race or the third
from the earlier conducted race where the fastest was the
first or the second from the earlier conducted race where
the second fastest from the 6th race was the first.....

So we have to find out the second and third from this group
by conducting the race between:

1)Second from the 6th race
2)Second from the earlier conducted race where the fastest
was the first
3)Third from the 6th race
4)Third from the earlier conducted race where the fastest
was the first
5)Second from the earlier conducted race where the second
fastest from the 6th race was the first

So after conducting this 7th race we will get the second
fastest and third fastest....

Hence the result is 7 races.......

Hope u will understand this.....
if not u can mail me