Question

there are 40 students in a class. 3 students are to be chosen as representatives. which is used here? permutation or combination?

Answer 1

i think combination .. combination is used for selection

Answer 2

so the answer would be \[\frac{40!}{3!37!}?\]

Answer 3

Yes ! i think so

Answer 4

so when do you use permutation?

Answer 5

combination , order doesn't matter.

Answer 6

so when to use permutation?

Answer 7

ppermutation is used with several slightly different meanings, all related to the act of permuting (rearranging) objects or values

Answer 8

combination is a way of selecting several things out of a larger group, where (unlike permutations) order does not matter.

Answer 9

source : http://en.wikipedia.org/wiki/Permutation
http://en.wikipedia.org/wiki/Combination

Answer 10

When you gotta choose people from a committee ---> COMBINATIONS
When you gotta find the number of ways to arrange(in different orders) ---> PERMUTATIONS

Answer 11

Well if the 3 positions were like special like they have specific roles it would be permutations i think :/

Answer 12

NO! Combinations

Answer 13

Number of ways to choose 3 people ---> 40 choose 3 ---> 40C3

Answer 14

Ze answer's in ze question!

"to be chosen" ----> choose -----> Combinations

If it had been some thing like "to be chosen and a queue be formed" and then the no. of ways to do this, then Mr. Permutation would have come into play.

Answer 15

ohhhhh...but i've seen some problems wherein there's no order specified but permutation was used...is that possible?

Answer 16

Can you post some examples of those questions?

Answer 17

it was long ago..i just saw a problem here that was answered that way...maybe it was just a wrong solution?

Answer 18

Permutation:

It is used when we have to select something and to arrange it too..

Combination:
It is used when we have to select only..

Answer 19

Wanna know the difference?
40C3 is the number of ways you could take out 3 people from 40 people.
40P3 is the number of ways you could take out 3 people from 40 people, AND ARRANGE THE 3 PEOPLE IN DIFFERENT ORDERS.

Answer 20

so let's say a committee..is that permutation or combination? it's combination right? because the members of a committee doesnt need to be arranged?

Answer 21

Yeah! :)

Answer 22

can you give an example of a permutation problem? i cant visualize it.. the one with the select and arrange thingy

Answer 23

The number of ways you could arrange 50 different markers in a packet is supposed to be 50P50.

Answer 24

The number of ways you could arrange 50 markers in a packet that can contain only 30 markers is 50P30.

Answer 25

but that's just arrange...i asked for *select* and arrange lol

Answer 26

Yep, see my second example. ;)

Answer 27

ohhhh

Answer 28

tthe combination couter part would be the number of ways you can put 50 markers in a packet that contains 30?

Answer 29

Yep.

Answer 30

great thanks :D

Answer 31

You're welcome! :)