finding the first 3 places in a car racing system...

[beemomo]

hi , everyone. I have a logical thinking question here to be solved, any help would be appreciated.

There are 25 racing cars in a car racing. The race tracks can only allow maximum 5 cars per session, i need to find out the fastest 3 racing cars (first place, second place and third place). How many session should i conduct for the cars to get the accurate result? and how should the calculation be done?
hint is that i only been told the answer is less than 10 times. I have been calculate it should be more than 10 times..still can't figure it out...
Hope u guys can help me...

[Stang02GT]

hi , everyone. I have a logical thinking question here to be solved, any help would be appreciated.

There are 25 racing cars in a car racing. The race tracks can only allow maximum 5 cars per session, i need to find out the fastest 3 racing cars (first place, second place and third place). How many session should i conduct for the cars to get the accurate result? and how should the calculation be done?
hint is that i only been told the answer is less than 10 times. I have been calculate it should be more than 10 times..still can't figure it out...
Hope u guys can help me...

25 cars 5 at a time = 5 sessions

take the top 3 cars from each session to race again = 15 cars

15 cars 5 at a time = 3 sessions

top three from each session = 9 cars

9 cars 3 at a time = 3 sessions

take the 1st place finisher from each session you have your top three racers

11 sessions total

[beemomo]

Dear Stang02GT,

I have proposed the same solution as u what u did just now, but this not the ideal anwser as the interviewer want the answer which is not more than 10.

Any idea on this? thanks ya

[Stang02GT]

I got it.


25 cars 5 at a time = 5 sessions

take the 1st place car from each session = 5 cars

make them race and take the top 3 from that race

for a total of 6 sessions

[Stang02GT]

I found another way to do this, but i haven't heard anything back as to weather my second answer works for you or not?

[RedSon]

I got it.


25 cars 5 at a time = 5 sessions

take the 1st place car from each session = 5 cars

make them race and take the top 3 from that race

for a total of 6 sessions

Why not just do 25 cars 5 at a time and then take the top three based on time? No need for the final session.

[Stang02GT]

Why not just do 25 cars 5 at a time and then take the top three based on time? No need for the final session.

I think there are about 20 different ways you can do this...thats another....i have about 4

[beemomo]

Dear Stang02GT and Red Son,

I need to apologize first as I am replying you guys very late because there is problem with my Internet connection.
Thank you very much for all your helps.

I manage to obtained one of the solution suggested by my friend.

************************************************** ******************************************
Firstly name each car with a number
--------------------
| 1 | 2 | 3 | 4 | 5|
| 6 | 7 | 8 | 9 | 10|
| 11| 12| 13| 14| 15|
| 16| 17| 18| 19| 20|
| 21| 22| 23| 24| 25|
---------------------
times used :5

Then race each group and we got this result :

--------------------
champion| 1 | 2 | 3 | 4 | 5|
second | 6 | 7 | 8 | 9 | 10|
third | 11| 12| 13| 14| 15|
--------------------

After that we race all car that get second place : 6,7,8,9,10
Then we get the top 3 answer, let said is 6,7,8 win...mean 9 and 10 lost.
Then we eliminate those low chances to win.

times used:6

now the diagram will become like that :
--------------------
champion| 1 | 2 | 3 | 4 | 5|
second | 6 | 7 | 8 |
third | 11| 12| 13|
-------------
Then we need to eliminate those low chance again...
No.6 may has chance to get second place in overall race. Now look at row 1, no.2 win no.7,no.7 get second place on last race, in other words no.7 can’t beat no.2 even it get second place on last race. So no.7 has the possibility to get 4th place in overall race. At this moment, we know that our diagram will become like this :
--------------------
champion| 1 | 2 | 3 | 4 | 5|
second | 6 |
third | 11|
-----

Then we race with 5 champion car.
Then the diagram will become:
-------------
champion| 1 | 2 | 3 |
second | 6 |
third | 11|
-----
times used:7

Then lastly, race again with no1, 2, 3, 6, 11 then will get the answer.

times used: 8

************************************************** ******************************************

As I know this is a logical test. I think there is no fixed answer or correct answer for the question, the tester might use the answer given by me to test my logical thinking concept.

Many thanks again for all your replies and answers. Cheers!