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asaf
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Identify permutation or combination? 1) In how many ways you 06 Oct 2006, 10:00
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Identify permutation or combination?

1) In how many ways you can invite 5 out of 10 friends to a dinner?

2) How many ways can you arrange 10 books on a bookshelf that has space for only 5?

3) A certain state lottery consists of selecting a set of 6 numbers randomly from a set of 49 numbers. To win the lottery, you must select the correct set of six numbers. How many possible lottery tickets are availble?

4) How many ways can 5 people sit on a park bench if the bench can only seat three people?



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Rayn
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Identify permutation or combination? 1) In how many ways you 06 Oct 2006, 10:04
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Correct me if I'm wrong but I think that they are all combination problems.
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chrismeiyu
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Identify permutation or combination? 1) In how many ways you 06 Oct 2006, 10:18
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yup - when dealing with combination problems, order does NOT matter.
So from the above problems, they are all combination b/c none of them require any kind of order.
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Rayn
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Identify permutation or combination? 1) In how many ways you 06 Oct 2006, 10:26
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Awesome thanks...
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jyotsnasarabu
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Identify permutation or combination? 1) In how many ways you 06 Oct 2006, 10:40
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This is my take on the given prob's

1). is a combination prob as the order taken is not important and we need to select five to invite them from 10 plp

so the answer according to my approach would be 10c5[c(10,5)]

2). here we use permutation, as the order is important. In an arrangement the order is always taken into consideration.

ans: 10p5

3). This on is definitely a combination problem

C(49,6)*6!*8 is my answer..........why 6!- is coz each set of the lottery has 6 no's associated with it and a total of 8 such sets exist.

4). this again is a permutation problem , since the order of arrangement matters

In short any problem that involves arrangement and order always comes under permutations.

Any problem that asks for selection is invariably a combination prob. here the arrangement does not matter

m not sure if the answers are correct though. It's just an attempt by me.
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asaf
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Identify permutation or combination? 1) In how many ways you 06 Oct 2006, 12:09
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Rayn
Correct me if I'm wrong but I think that they are all combination problems.
Show more


not all of them are combos..
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londonluddite
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Identify permutation or combination? 1) In how many ways you 06 Oct 2006, 12:23
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my take:

1. combo
2. perm
3. combo
4. perm

combo - arrangment does not matter, perm it does



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