Permutations (1 Viewer)

[lwyhws]

Need help in arrangements in a circle.

Can anyone help me with these kinda q's...

(P187 Q10, 3u Fitzpatrick)
In how many ways can 6 people be arranged in a circle if 2 particular people are always:
a) together?
b) separated?

I understand part a) but have no clue in part b). Can someone please explain the working. Thanks alot

 

[acmilan]

The total arrangements in a circle when you dont care about where anyone sits is (6-1)! = 5!. Now you know the answer to part (a), where they are together. If they are not sitting together, then they must be sitting separated. Hence all the permutations that arent in part (a) are the ones where they arent together, ie. (total permutations) - (permutations when they are together).

 

[lwyhws]

It makes sense now. Thanks!

 

[pLuvia]

can someone explain to me what the point of permutations is for/

 

[acmilan]

can someone explain to me what the point of permutations is for/

Counting methods? Probability? Does that sound familiar? They also play a role in matrix algebra.

 

[SDuke]

lwyh your avatar looks awfully similar to my skool crest, where it u get the it?

 

[withoutaface]

can someone explain to me what the point of permutations is for/

Permutations are a special kind of function whereby it creates a bijective map from a set to itself.

 

[lwyhws]

lol its cut out from a st.george illawarra banner! go the dragons

 

[need_notes]

ummmm...do u know the answer 2 dis and how u can get it:
u have the digits:2, 3, 4, 5, 6 and 7:
-In how many ways can and even number be made from these digits

 

[withoutaface]

well you can have 1 digit, 2, 3, 4, 5 or 6 digits.

1 digit

3 numbers

2 digits

(going from last digit to first digit) 3*5

3 digits

3*5*4

4 digits

3*5*4*3

5 digits

3*5*4*3*2

6 digits

3*5*4*3*2*1

For the final answer you add all these up.

 

[wanton-wonton]

Permutations are a special kind of function whereby it creates a bijective map from a set to itself.

Yeah, that definition is really going to help him.

 

[need_notes]

im sorry about this but i forgot to mention one important aspect of the question....a 3 digit number is to be made with the numbers 2, 3, 4, 5, 6, 7 (and the rest of the question is the same)

 

[MarsBarz]

im sorry about this but i forgot to mention one important aspect of the question....a 3 digit number is to be made with the numbers 2, 3, 4, 5, 6, 7 (and the rest of the question is the same)

Are you allowed to repeat digits? For example would 332 be valid?

 

[MarsBarz]

Numbers:2,3,4,5,6,7
Must end with even number, ie:2 or 4 or 6

Repetition allowed:
6*6*3

 

[withoutaface]

Not quite. 6*6*3.

 

[need_notes]

thanx for your help...newaiz how about repetition?(what do u mean by that) and whateva it is, what if were not allowed to occur what would a possible answer be? thanx again 4 all ur help

 

[withoutaface]

Repetition means that a number such as 666 or 424 etc is possible.

If repetition were not allowed the answer would be 3*5*4

 

[need_notes]

thank you very much...u have been a big help...cheers...n laterz

 

[need_notes]

just 2 let u know that i know it and all....u have 3 numbers that are even so u choose 1 of them (so we have 3) then u will have 5 numbers left 2 choose 4rom and we choose 1 of them (so we have 3x5) and finally we will be left with 4 numbers to choose from and we choose one number (so we end up with 3x5x4=60) thanx alot

 

[richz]

lol, permutations and combinations is my worst topic, have no fuken idea wat is going on