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/sci/ - Science & Math

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7253223 No.7253223 [Reply] [Original]

Why are combinations and permutations so hard ;_;

>> No.7253234

>>7253223
Because they aren't.

>> No.7253240

>>7253234
For me they are :(

>> No.7253273

>>7253223
http://www.learner.org/courses/mathilluminated/units/2/textbook/01.php

Read that and see if it helps. I'm going through it because im retarded and need to re-learn this shit.

>> No.7253286

>>7253240
:(((

>> No.7253288

for me it's when you start thinking about whether a situation calls for considering distinguishable or indistinguishable objects that it's easy to get befuddled

>> No.7253294

>>7253223
Read the proofs of the equations. Unless you already have, rest in pieces, m8.

>> No.7253301

>>7253223
Don't focus too much on the mathematical notation -- it hasn't even been completely standardized, if your pic is any indication.

Instead, look around you for examples of permutations and combinations, and latch on to those for intuition. Shuffle a deck of cards. Sort people into groups, select meal combinations from a menu. That sort of thing.

>> No.7253304

>>7253223
Ivan niven wrote a very easy introduction to the subject, its full of exercises and worked examples. Its very elementary, i think its called count without counting or something like that.

>> No.7253325

OP here I fucking give up. Fuck Business math and these gay ass word problems. I don't even want to be a business major anymore. Fuck why did I take this class instead of a pure math class like Calculus. Just fuck my shit up.

>> No.7253349

>>7253325
combinations are permutations are very important in pure math, specifically combinatorics, too. lol.

>> No.7253469

>>7253349
Not really in Calculus though.

>> No.7253479

https://www.mathsisfun.com/combinatorics/combinations-permutations.html

fun!

>> No.7253484

>>7253349
Dude I'm talking about the business applications of combinations and permutations and the stupid word problems that are what make it hard for me.

>> No.7253649

>>7253301
This is the answer. It also happens to be the answer of how to understand most things in math and physics

>> No.7253681
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7253681

>>7253469
They show up in calculus too, bud.

>> No.7253921

>>7253681
When do they show up, in entry level Calculus classes?

>> No.7253934

>>7253921
They'll probably show up when you do infinite sequences and series.

>> No.7253949

>>7253934
Nah not gonna do it

>> No.7253978

>>7253484
Dude the word problems are important even if you pursue pure math (in probability) for example... It should not take you long to translate a word problem into a formal mathematical question. The fact that you struggle with that may be a sign of a lack of basic problem-solving skills or familiarity with english, which are both serious red flags.

>> No.7253992

>>7253978
Yes those would be red flags, if I were pursuing a degree in mathematics. I'm doing a degree in mechanical engineering.

>> No.7254018

>>7253992
But all problems in physics are word problems, and they're much harder because there are many ways to understand the same question.

>> No.7254031

>>7254018
I'm doing mech engineering not physics dude. Physics is easy anyway. You are just given values and then you plug them into a formula. Easy.

>> No.7254040

number of permutations of n objects - n! (n options for first option, n-1 for second, ...)
number of permutations for r objects chosen from n - n options for first option, n-1 for second, ..., down to (n - r + 1) for rth. then altogether, you have (n)(n-1)...(n-r+1) = n!/(n-r)!
for n choose r, you just divide out r! to get rid of the number of permutations for each selection of r objects

>> No.7254041

>>7254031
Yeah but sometimes you aren't given all the values and you have to deduce them from other related values....

>> No.7254049

>>7254041
Can't be that hard.

>> No.7254058
File: 859 KB, 500x270, tumblr_inline_mi0xmwDBsK1qz4rgp.gif [View same] [iqdb] [saucenao] [google]
7254058

>>7254041
We call that algebra.

>> No.7254187

>>7253921
Taylor series.

>> No.7254666
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7254666

>>7253223
there are some useful sayings that helped me understand it when i took graduate probability

N Choose R

N P(something) R

>> No.7254677

>>7253223
if something is hard it means you just need more practice. at one point walking was hard for you.

>> No.7254748

>>7254677
im a dumb little bitch. I shouldnt need practice

>> No.7254794

Because you don't know how to count

>> No.7254808

>>7254666
N Permute R, or N Partial R (ie, partial permutations that are nontrivial on exactly R elements of the set with cardinality N).

>> No.7254835
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7254835

>>7254677

>> No.7254892

Although the concepts aren't too hard, they word them like shit

>> No.7255125

>>7254666
>>7253223
N Choose R (as in, you can only choose one thing once, its only the order that matters)
N Pick R (as in, you can pick something as many times as you want, in any order)