#C&P

134 messages · Page 1 of 1 (latest)

vestal niche
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In how many ways can 4 pieces of candy be given to 3 kids if the candy is distinguishable, and the kids are indistinguishable?

I'm understanding that there are four cases:

C1) {4, 0, 0}
C2) {3, 1, 0}
C3) {2, 2, 0}
C4) {2, 1, 1}

  1. The first case is obviously just one since there is only one way for the children who are indistinguishableto be given four candies.
  2. I believe this would be 4!/3! so four.
  3. 4!/2! gives me six.

Case three stumps me

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vestal niche
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Help as soon as possible would be appreciated, but this is just a problem I stumbled upon and struggle to wrap my head around...

vestal niche
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I would also assume that case 3 would equal 6, but the correct answer does not seem to be 17

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@mild raptor you have any suggestions on this one?

vestal niche
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Nvm solved it

dawn coyote
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Are we required to distribute all of the candies to the children, or do we have to do cases where we distribute, say, only A, only B, only C, only D, only A and B... etc?

sturdy girder
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All your other cases are right, you have to add these cases to get the total number of ways

sturdy girder
vestal niche
sturdy girder
vestal niche
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I think I did

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14

sturdy girder
vestal niche
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But could you explain a little more about why 4!/2!2!

vestal niche
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The third case atleast

sturdy girder
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How is 4!/2!=6?

vestal niche
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Noo

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Why you got 4/2!2!

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4!/2!2!

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Instead of just 4!/2!

sturdy girder
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That's what you wrote in case 4 of your answer

vestal niche
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Oh wait

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Nvm

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I was thinking about a dif one

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Yeah

sturdy girder
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Wait I'll tell you, you wrote 4!/2!=6

vestal niche
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The repeats are because if I have candies AB

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CD is forced

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And as such

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CD AB is forced

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Right?

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Am I going about this the wrong way

sturdy girder
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I don't understand your explaination here, so nk idea

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What I think is $1 + \frac{4!}{3!1!} + \frac{4!}{2!2!} + \frac{4!}{2!1!1!} = 1+4+6+12 = 23$

night jungleBOT
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fäf kaka

sturdy girder
# vestal niche Yes

Well do you know the method where we find number of ways $r$ digits add up to $n$?

night jungleBOT
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fäf kaka

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fäf kaka

vestal niche
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Unsure

sturdy girder
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Wait, I'll show you

vestal niche
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Oh stars and bars

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Yea

sturdy girder
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If we go by this, then we get ${4+3-1 \choose 4-1} = {6 \choose 3} = 20$

vestal niche
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That doesn’t work in this case because

night jungleBOT
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fäf kaka

vestal niche
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The candies are distinguishable

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But the children were not

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If it were the other way around I believe it would work though

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Atleast that’s what I remeber

sturdy girder
vestal niche
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Stars and bars work

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When k is distinguishable

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But it isn’t in this case

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The candies are

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It’s like saying put 0 kids in a candy

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Or one kid

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No?

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I could just be wrong.

sturdy girder
vestal niche
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The correct answer does seem to be 14

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@dawn coyote could you explain your process to me?

vestal niche
# vestal niche Yes

All candies must be distributed amongst the children but any child is not required to have candy

dawn coyote
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So, like, let's define the set S = {A, B, C, D}.

vestal niche
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Yes

dawn coyote
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Then we want to construct the set X of all sets Y such that:

  1. Y is a subset of the powerset of S.
  2. |Y| = 3.
  3. The intersection between any two elements of Y is empty.
  4. The union of all elements of Y is S.
vestal niche
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Why would the absolute value of y be 3?

dawn coyote
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Three children, right?

vestal niche
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Ohh

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Okay

dawn coyote
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...wait. Okay, that doesn't work, because Y = {{A, B, C, D}, 0, 0} should be in X, but isn't, because by extensionality it actually only has a magnitude of 2.

vestal niche
dawn coyote
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Well, whatever. We can construct X as I've defined it and just add one to the cardinality, which is the part of X we care about.

vestal niche
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Alright, I think I kinda get it so far

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I’m thankful for your hope ur unfortunately I must go eat dinner, um hopefully you could explain your solution whenever you feel as if you had time and I can read it when I get back?

sturdy girder
dawn coyote
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Hmm. Okay, so the way I think about it is, there's one quartet in P(S), right? Which corresponds to one child getting all four candies.

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There's four triplets.

sturdy girder
dawn coyote
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Corresponding to one child getting three of the candies and a second child getting the fourth.

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Since we don't care which child gets which set of candies, there is only one distribution for each triplet.

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Then there's six couples. This is where it gets complicated, because each couple can be paired with either a couple or two singles.

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So, let's see. That's six couple/single/single sets and three couple/couple pairs (since couple pairs are isomorphic on permutation, thus the six couple pairs get divided in half). So that's 1 + 4 + 6 + 3 = 14. And we can't do anything with the singletons because every possible combination of singletons was already accounted for.

vestal niche
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the difference is that the kids we are distributing to are indishtinguable

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so no

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how what

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you cant put

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a kid in a candy

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which is also why stars and bars dont work

dawn coyote
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...what?

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...to... candies...?

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But each candy can only be distributed to one kid.

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...no, I'm saying 3000 doesn't work. That's distributing Candy A to all three kids, and candies B, C, and D to none, right?

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But Candy A can only go to one kid, and B, C, and D must go to a kid.

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I mean, that's what I did. I'm sure there's probably a more efficient way, but it would have to come out to the same answer.

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And your approach is irreparably flawed.

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No offense.

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...it's literally the last thing said in the channel before you got here.

dawn coyote
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What "211 case"?

dawn coyote
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That doesn't help me.

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That would be a doubleton and two singletons. There are six doubletons (4C2), and each has only a single pair of singletons that complete the distribution, so... there's six.

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...what?

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No.

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Where's the other six coming from?

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There are only three of those.

dawn coyote
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...because {{A, B}, {C, D}} = {{C, D}, {A, B}}

dawn coyote
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...why 4c2?

dawn coyote
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...but we were talking about 2, 2, 0.

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Except, again, {{A, B}, {C, D}, 0} = {{C, D}, {A, B}, 0}.

dawn coyote
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^

vestal niche
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As long as any two candies are chosen first, it forced to the other person having two candies, as such they have the same probability and why divide by two

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In my mind that’s how I saw it

dawn coyote
vestal niche
dawn coyote
vestal niche
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Sorry

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😭

dawn coyote
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Wait.

vestal niche
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?

dawn coyote
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Sorry. Didn't realize I was explaining to two different people.

vestal niche
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xd

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All g

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Imma close the post now

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Thanks tho 🙏

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+close