Question

Counting Surjections with Inclusion-Exclusion

score 2.6k · Answer 1 · 2019-02-17 23:05:02

2.6k

Views

Counting Surjections with Inclusion-Exclusion

Published on 17 Feb 2019 - 23:05

score 45 · Answer 2 · 2019-02-18 00:37:30

45

Views

Principle of I/E: In how many ways can eight cakes be distributed among four kids if every kid receives at least one cake?

Published on 18 Feb 2019 - 0:37

score 392 · Answer 3 · 2019-02-25 23:12:57

392

Views

Showing an alternating sum is positive

Published on 25 Feb 2019 - 23:12

score 75 · Answer 4 · 2019-02-26 03:07:44

75

Views

How many numbers between $1 - 1000$ leave no remainder when divided by $4$ and when divided by $6$ but not when divided by $21$?

Published on 26 Feb 2019 - 3:07

score 66 · Answer 5 · 2019-03-01 08:06:19

66

Views

Calculate $\sum_{|S|=k}(n-|\cup S|)^m$ where $S$ is a subset of $X=\{\{a_1,a_2\},\{a_2,a_3\},\cdots,\{a_{n-1},a_n\},\{a_n,a_1\}\}$

Published on 01 Mar 2019 - 8:06

score 41 · Answer 6 · 2019-03-03 15:57:06

41

Views

Why does taking floored root of a natural number x give me all natural numbers up to x which are perfect squares,cubes,fifths etc.

Published on 03 Mar 2019 - 15:57

score 696 · Answer 7 · 2019-03-05 16:00:11

696

Views

Reverse Inclusion - Exclusion Principle

Published on 05 Mar 2019 - 16:00

score 243 · Answer 8 · 2026-03-25 20:11:58

243

Views

How to count all the solutions for $\sum\limits_{i=1}^{n} \frac{1}{2^{k_i}}= 1$ for $k_i\in \Bbb{N}$ and $n$ a fixed positive integer?

Published on 25 Mar 2026 - 20:11

score 264 · Answer 9 · 2019-03-11 09:24:41

264

Views

How many permutations are there of M, M, A, A, A, T, T, E, I, K, so that no two consecutive letters are the same?

Published on 11 Mar 2019 - 9:24

score 2.2k · Answer 10 · 2019-03-16 16:23:59

2.2k

Views

Positive Integers between 100 and 999 inclusive that are divisible by 3 but not by 4?

Published on 16 Mar 2019 - 16:23

score 90 · Answer 11 · 2019-03-16 23:07:02

90

Views

Notation for "or" in inclusion-exclusion formula

Published on 16 Mar 2019 - 23:07

score 865 · Answer 12 · 2019-03-18 18:02:45

865

Views

What is the probability that no 2 books from the same major will be placed next to each other?

Published on 18 Mar 2019 - 18:02

score 755 · Answer 13 · 2019-03-20 21:30:54

755

Views

Colouring the sides of a hexagon

Published on 20 Mar 2019 - 21:30

score 331 · Answer 14 · 2026-03-25 21:00:09

331

Views

An explicit "formula" for the prime counting function?

Published on 25 Mar 2026 - 21:00

score 288 · Answer 15 · 2019-03-27 03:07:53

Told by Professor that this is PIE, but don't see how it's PIE. Help understanding what constitutes the sets, or alternative ways to solve?

List Question

Counting Surjections with Inclusion-Exclusion

Principle of I/E: In how many ways can eight cakes be distributed among four kids if every kid receives at least one cake?

Showing an alternating sum is positive

How many numbers between $1 - 1000$ leave no remainder when divided by $4$ and when divided by $6$ but not when divided by $21$?

Calculate $\sum_{|S|=k}(n-|\cup S|)^m$ where $S$ is a subset of $X=\{\{a_1,a_2\},\{a_2,a_3\},\cdots,\{a_{n-1},a_n\},\{a_n,a_1\}\}$

Why does taking floored root of a natural number x give me all natural numbers up to x which are perfect squares,cubes,fifths etc.

Reverse Inclusion - Exclusion Principle

How to count all the solutions for $\sum\limits_{i=1}^{n} \frac{1}{2^{k_i}}= 1$ for $k_i\in \Bbb{N}$ and $n$ a fixed positive integer?

How many permutations are there of M, M, A, A, A, T, T, E, I, K, so that no two consecutive letters are the same?

Positive Integers between 100 and 999 inclusive that are divisible by 3 but not by 4?

Notation for "or" in inclusion-exclusion formula

What is the probability that no 2 books from the same major will be placed next to each other?

Colouring the sides of a hexagon

An explicit "formula" for the prime counting function?

Told by Professor that this is PIE, but don't see how it's PIE. Help understanding what constitutes the sets, or alternative ways to solve?

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