On a race track a maximum of 5 horses can race together at

Bunuel,

It is uncertain to me that how we can be sure to pick horses for 7th race..

Isn't a possibility that second horse from Gold Medal winner group can be slower than the second horse in Bronze Medal winner group?

Lets say: The Gold medal horse took 2 mins, second horse in the Gold medal group took 5 mins to cover the race. While Bronze medal horse took 3 mins and second horse from Bronze medal group took 4 mins.

In that case, we need to change this:
"second horse from the first round race with the Gold medal winner;" with "second horse from the first round race with the Bronze medal winner;"

Please, explain.

On a race track a maximum of 5 horses can race together at a time. There are a total of 25 horses. There is no way of timing the races. What is the minimum number of races we need to conduct to get the top 3 fastest horses?

A)5
B)7
C)8
D)10
E)11

On every race we get the top 3 out of 5.

First 5 Races = Take 3 from each race = 15
Next 3 Races = Take 3 from each race = 9
At this point I figured that we only need 3 horses and we have 2 races. So take the top 2.
Next 2 Races = Take 2 from each race = 4
Last race we get the top 3.

Total races = 5+3+2+1 = 11
Answer = E

I came down to 7. I mean that I can do the task in 7 races.

First 5 races: all horses by five. We'll have the five winners.

Race 6: the winners of previous five races. We'll have the 3 winners.
Now it's obvious that #1 here is the fastest one (gold medal).
For the silver and bronze we'll have 5 pretenders:
1. #2 from the last sixth race,
2. #3 from the last sixth race,
3. the second one from the race with the Gold medal winner from the first five races,
4. the third one from the race with the Gold medal winner from the first five races,
5. the second one from the race with the one which took the silver in the sixth race

Race 7: these five horse: first and second in this one will have the silver and bronze among all 25.

Answer B (7).

Good Q. +1

For the silver and bronze we would have 5 pretenders:
1. #2 from the 6th race;
2. #3 from the 6th race;
3. the second horse from the first round race with the Gold medal winner;
4. the third horse from the first round race with the Gold medal winner;
5. the second horse from the first round race with horse #2 in the 6th.

So total 7 races are needed.

The trick here is that we should choose the horses for the last race so that each horse to be pretender for either the Silver or the Bronze medal.

Now, second horse from the first round race with horse #3 in the 6th race could be faster than the second horse from the first round race with the Gold medal winner, but if it is so could this horse get any medal? It's obviously slower than horse #3 and also slower that horse #2 (from the last race) so there is no sense to include this horse in the last race. Similar logic works for other horses.

Hope it's clear.

I came down to 7. I mean that I can do the task in 7 races.

First 5 races: all horses by five. We'll have the five winners.

Race 6: the winners of previous five races. We'll have the 3 winners.
Now it's obvious that #1 here is the fastest one (gold medal).
For the silver and bronze we'll have 5 pretenders:
1. #2 from the last sixth race,
2. #3 from the last sixth race,
3. the second one from the race with the Gold medal winner from the first five races,
4. the third one from the race with the Gold medal winner from the first five races,
5. the second one from the race with the one which took the silver in the sixth race

Race 7: these five horse: first and second in this one will have the silver and bronze among all 25.

Answer B (7).


Good Q. +1

I came down to 7. I mean that I can do the task in 7 races.

First 5 races: all horses by five. We'll have the five winners.

Race 6: the winners of previous five races. We'll have the 3 winners.
Now it's obvious that #1 here is the fastest one (gold medal).
For the silver and bronze we'll have 5 pretenders:
1. #2 from the last sixth race,
2. #3 from the last sixth race,
3. the second one from the race with the Gold medal winner from the first five races,
4. the third one from the race with the Gold medal winner from the first five races,
5. the second one from the race with the one which took the silver in the sixth race

Race 7: these five horse: first and second in this one will have the silver and bronze among all 25.

Answer B (7).

Good Q. +1

Hi Bunnel,

Is this a GMAT-kind question?

Isn't it possible to make just one race?
All the horses run the same track, and after 5 races we can get the results for all horses.
Now we can just choose based on the timing the top 3 fastest horses.....
Why is this wrong?

On a race track a maximum of 5 horses can race together at a time...