combinatorics | Mathematics | Page 1

fathom tinsel Dec 27, 2025, 1:10 PM

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for question 9 are they immediately adjacent or are there still ways to order those three girls

warm fogBOT Dec 27, 2025, 1:10 PM

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fathom tinsel Dec 27, 2025, 1:12 PM

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does anybody have like another interpretation of this q i feel like i misinterpreted it

merry badger Dec 27, 2025, 1:15 PM

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fathom tinsel does anybody have like another interpretation of this q i feel like i misinterpr...

looks good until they mean they can be not together

fathom tinsel Dec 27, 2025, 1:16 PM

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so i cant arrange them in any more ways

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its just always ronnie annie rachel

merry badger Dec 27, 2025, 1:16 PM

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like Ron- Person-An-Person-Rach -Person

merry badger Dec 27, 2025, 1:17 PM

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fathom tinsel its just always ronnie annie rachel

yeah their arrangement wrt each other is fixed

fathom tinsel Dec 27, 2025, 1:17 PM

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omg ok ty

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is my answer right

merry badger Dec 27, 2025, 1:17 PM

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merry badger like Ron- Person-An-Person-Rach -Person

but if u consider this

merry badger Dec 27, 2025, 1:18 PM

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fathom tinsel is my answer right

that's why i need you to check

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so we know what they mean

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if you have answer key

fathom tinsel Dec 27, 2025, 1:19 PM

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who the hell is sanjay

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it wasnt in the og question

merry badger Dec 27, 2025, 1:23 PM

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we good then

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answer matches

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wud you like to try cases they are not together @fathom tinsel

fathom tinsel Dec 27, 2025, 1:26 PM

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yes

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plz

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would u just leave gaps in between them

merry badger Dec 27, 2025, 1:27 PM

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hmm.. gaps approach is good

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but you get cases

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like you can put 2 gapsbetween two people

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or 1 gap or none,
like Ronn P1 P2 An P3 Rach
Ronn P1 An P2 Rach P3
Ronn An P1 Rach P2 P3

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you can have either two ppl between or 1 or none

fathom tinsel Dec 27, 2025, 1:31 PM

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wait then how would u approach those kind of problems then

merry badger Dec 27, 2025, 1:32 PM

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hmm..

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how wud u arrange all 6 without conditions

fathom tinsel Dec 27, 2025, 1:33 PM

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6!

merry badger Dec 27, 2025, 1:33 PM

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right

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we know only one order of Ronn An Rach exists

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we try to cancel all other orders

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we divide 6!/3!

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did you understand

fathom tinsel Dec 27, 2025, 1:37 PM

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ohhhhhh thats so much easier than doing gaps

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ceebs to list all the gaps out

merry badger Dec 27, 2025, 1:38 PM

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fr

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more difficult with higher numbers

merry badger Dec 27, 2025, 1:39 PM

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merry badger we divide 6!/3!

tho did you understand why?

fathom tinsel Dec 27, 2025, 1:40 PM

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to cancel the ways theyre together?

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like to get rid of the arrangements theyre together

merry badger Dec 27, 2025, 1:44 PM

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fathom tinsel like to get rid of the arrangements theyre together

mm.. yeah

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look this :
X P1 X P2 X P3 this is one of the 6! position
X are the positions we put the 3
here we can arrange them in only 1 way raher than 3!
this is for all cases hence we divide all of them by 3!

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Ron P1 An P2 Rach P3
Ron P1 Rach P2 AnP3
AnP1 Ron P2 Rach P3
.....
we need only one of these 6 arrangements

fathom tinsel Dec 27, 2025, 1:50 PM

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thanks so much bro bros clutching my maths marks next yr 💔

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also

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do u know whats the default for permutation qs like if it doesnt specify w or wo repetition which one do i do?

merry badger Dec 27, 2025, 1:53 PM

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fathom tinsel do u know whats the default for permutation qs like if it doesnt specify w or wo...

depends on q generally without

fathom tinsel Dec 27, 2025, 1:59 PM

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Like for this q

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also does inclusion exclusion apply to c

merry badger Dec 27, 2025, 2:06 PM

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fathom tinsel

consider repetition for a

merry badger Dec 27, 2025, 2:06 PM

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fathom tinsel also does inclusion exclusion apply to c

why

fresh verge Dec 28, 2025, 2:27 AM

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merry badger consider repetition for a

in (b) the phrase “no character being used more than once” explicitly forbids repetition right..

fresh verge Dec 28, 2025, 2:29 AM

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fathom tinsel also does inclusion exclusion apply to c

inclusion exclusion isn’t needed here because 4 letters and 3 letters + 1 digit are mutually exclusive cases so we just add them

fresh verge Dec 28, 2025, 2:34 AM

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fathom tinsel

also for (b) 26 x 25 x 10 x 9 only counts one specific arrangement (namely LLDD) but since a password is ordered you must multiply by the other possible positions of the letters and digits (eg LLDD, LDLD, LDDL, DLLD, DLDL, DDLL)

merry badger Dec 28, 2025, 5:50 AM

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fresh verge in (b) the phrase “no character being used more than once” explicitly forbids re...

right mb i didn't read

fathom tinsel Dec 29, 2025, 4:49 AM

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.close

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