#Combinatorics Help

72 messages · Page 1 of 1 (latest)

autumn wedge
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Find the number of 5-lists of the form (x1, x2, x3, x4, x5), where each xi
is a nonnegative integer and x1 + x2 + x3 + x4 + 3x5 = 12.

dull estuaryBOT
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autumn wedge
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So far what i did is substitute x5 for 0,1,2,3,4 and create new equations

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which are

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a + b + c + d = 12
a + b + c + d = 9
a + b + c + d = 6
a + b + c + d = 3
a + b + c + d = 0

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where a is x1, b is x2 and so on

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now the problem is getting the amount of probabilities for each

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the last one is obviously 1

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but then the rest is terrifying

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for the penuultimate equation i got 19

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bc

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if all were 1 except for one value

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itd be 6 ways

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there are 12 ways to arrange 2 and 1

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and 1 way to arrange 3

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6 = 5 + 1
= 4 + 2
= 3 + 3

autumn wedge
autumn wedge
autumn wedge
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this can be broken down into

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3 + 1 + 1 + 1, 2 + 2 + 1 + 1,

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AND U HAVE TO FIND THE POSSIBILITIES OF ALL OF THEM

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AND THEN REPEAT THIS AGAIN

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FOR 2 MORE TIMES

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BUT MORE COMPLEX 😭

autumn wedge
autumn wedge
autumn wedge
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i can't do this again and again 😭

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wait is the answer 4^4?

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love how im talking to myself

autumn wedge
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DID ALL THAT FOR ME TO RELAIZE

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BTW THE WAY I GOT IS

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N^R

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in order matter no matter repitiion no repittion table thingy

autumn wedge
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and nvm

peak moss
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you can start by considering the possibilities for x5 (0 to 4) and then just stars and bars the rest

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@autumn wedge

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sorry i thought someone already helped you from the message count lol

autumn wedge
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oh

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lol

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thx

peak moss
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do you know stars and bars?

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or balls and bars

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whatever

autumn wedge
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is it like

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that thingy

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((n))

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that thing

peak moss
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wha

autumn wedge
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uh

peak moss
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no its like uhh
i want 5 scoops of icecream and there are 3 flavours avaliable

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how many different combinations of flavours can i get

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and then you do

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ooooo||

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and then like uh

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| separates the number of flavour of one kind

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so oo|o|oo means tehres 2 of flavour 1, 1 of flavour 2, 2 of flavour 3

peak moss
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familiar or nah

autumn wedge
autumn wedge
autumn wedge
peak moss
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yea

autumn wedge
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didnt think to use it 😭

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EVEN THOUGH I JUST LEARNT IT AND THAT WAS A PRAC OPROBLEM

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im actually sped