Find all School-related info fast with the new School-Specific MBA Forum

 It is currently 14 Sep 2014, 18:39

### GMAT Club Daily Prep

#### Thank you for using the timer - this advanced tool can estimate your performance and suggest more practice questions. We have subscribed you to Daily Prep Questions via email.

Customized
for You

we will pick new questions that match your level based on your Timer History

Track

every week, we’ll send you an estimated GMAT score based on your performance

Practice
Pays

we will pick new questions that match your level based on your Timer History

# Events & Promotions

###### Events & Promotions in June
Open Detailed Calendar

# i have struggled with the concepts of permutations and

Author Message
TAGS:
Intern
Joined: 05 Oct 2008
Posts: 11
Followers: 0

Kudos [?]: 0 [0], given: 0

i have struggled with the concepts of permutations and [#permalink]  22 Dec 2008, 01:58
i have struggled with the concepts of permutations and combinations since high school.

i still do not understand when order matters and when it does not. for example,:
How many ways are there to award a gold, silver and bronze medal to 10 contending teams?

does order matter here?

If we name the teams A to J
A B C D E F G H I J
1 2 3 n n n n n n n

within teams A, B and C, does it matter who gets 1 - gold, 2 - silver, 3 - bronze?

In a room filled with 7 people, 4 people have exactly 1 friend in the room and 3 people have exactly 2 friends in the room (Assuming that friendship is a mutual relationship, i.e. if John is Peter's friend, Peter is John's friend). If two individuals are selected from the room at random, what is the probability that those two individuals are NOT friends?

does order matter here?

is there anyone who is able to explain these concepts to me in a simple manner? ive tried everything to try and figure them out but it seems impossible. and i HAVE to figure out when order matters because the formulae are different where order matters and where it doesnt.

HELP.
Senior Manager
Joined: 06 Mar 2006
Posts: 497
Followers: 7

Kudos [?]: 76 [0], given: 1

Re: When does order matter [#permalink]  22 Dec 2008, 19:17
When you select people for gold, silver, and bronze medal, yes, order matters.

When you randomly select 3 people out of 7, then no, order does not matter.
CEO
Joined: 29 Aug 2007
Posts: 2501
Followers: 53

Kudos [?]: 505 [0], given: 19

Re: When does order matter [#permalink]  23 Dec 2008, 09:23
sidrah wrote:
i have struggled with the concepts of permutations and combinations since high school.

i still do not understand when order matters and when it does not. for example,:
How many ways are there to award a gold, silver and bronze medal to 10 contending teams?

does order matter here?

If we name the teams A to J
A B C D E F G H I J
1 2 3 n n n n n n n

within teams A, B and C, does it matter who gets 1 - gold, 2 - silver, 3 - bronze?

Here order matters because the way the medals are distributed varies as the order changes. for ex:

* A (Gold), B (Silver) and C (Bronze), and B (Gold), A (Silver) and C (Bronze) are two different ways. Therefore, order matters in this case.

No of people who can get gold medal = 10
No of people who can get silver medal = 10 - 1 = 9
No of people who can get silver medal = 10 - 1 - 1 = 8
so total number of ways the medals can be given = 10x9x8 = 720

Permutation:

When order matters i.e. called permutation. The formula for the permutation is npr = n!/(n-r)! = 10p3 = 10!/(10-3)! = 10x9x8x7!/7! = 720

sidrah wrote:
In a room filled with 7 people, 4 people have exactly 1 friend in the room and 3 people have exactly 2 friends in the room (Assuming that friendship is a mutual relationship, i.e. if John is Peter's friend, Peter is John's friend). If two individuals are selected from the room at random, what is the probability that those two individuals are NOT friends?

does order matter here?

is there anyone who is able to explain these concepts to me in a simple manner? ive tried everything to try and figure them out but it seems impossible. and i HAVE to figure out when order matters because the formulae are different where order matters and where it doesnt.

HELP.

This is a case of combination.

When order doesnot matter, that is combination. In combination, we are combining a given number of people. Therefore, it cannot have an order. 3 people in a group is is always a group no matter we arrange them.

For ex: 10 people are divided in a group of 3 each.
no of group (combination) = 10c3 = 10!/(3!)(10-3)! = 30
_________________
Re: When does order matter   [#permalink] 23 Dec 2008, 09:23
Similar topics Replies Last post
Similar
Topics:
4 I have just attempted to compile a concept of an Exception 6 28 Mar 2011, 22:02
1 Struggling with Math Concepts and Application - Advice? 1 02 Aug 2010, 11:43
I'm having trouble with the rule behind this concept. This 10 07 Sep 2008, 15:24
I have been struggling with the RC Inference questions. They 1 18 Jul 2008, 13:33
I'm struggling to get the coordinate concept ironed out. Is 2 02 Jun 2008, 06:32
Display posts from previous: Sort by