Question

How many strings of length $10$, with letters taken from $\{A, B, C, D, E\}$, contain at least $1$ $A$ and at least $1$ $B$?

score 107 · Answer 1 · 2026-04-16 02:13:56

107

Views

How many strings of length $10$, with letters taken from $\{A, B, C, D, E\}$, contain at least $1$ $A$ and at least $1$ $B$?

Published on 16 Apr 2026 - 2:13

score 826 · Answer 2 · 2026-04-15 03:49:40

826

Views

Every graph $G$ with $d(G) \ge 4k$ has a $(k + 1)$-connected subgraph $H$ such that $\epsilon (H) > \epsilon(G) − k$.

Published on 15 Apr 2026 - 3:49

score 158 · Answer 3 · 2026-04-23 01:27:36

158

Views

Is the set of extensive, increasing, ∅-preserving operators 2^X→2^X closed under composition?

Published on 23 Apr 2026 - 1:27

score 217 · Answer 4 · 2026-04-13 14:34:29

217

Views

Analysis of super-structures emerging in a spiral representation of prime numbers

Published on 13 Apr 2026 - 14:34

score 76 · Answer 5 · 2026-04-15 14:29:39

76

Views

Recurrence Relation of Stirling number of second kind.

Published on 15 Apr 2026 - 14:29

score 209 · Answer 6 · 2026-04-11 11:22:57

209

Views

combinatorics: a variant of set covering/subset selection problem?

Published on 11 Apr 2026 - 11:22

score 871 · Answer 7 · 2026-04-13 22:57:03

871

Views

Digits of a number and the probability of product of the digits being even

Published on 13 Apr 2026 - 22:57

score 382 · Answer 8 · 2026-04-15 07:46:15

382

Views

$\sum_{j=1}^n \sum_{k=j+1}^n (1)$

Published on 15 Apr 2026 - 7:46

score 65 · Answer 9 · 2026-04-11 08:06:57

65

Views

How many exam papers earn a grade of $90%$

Published on 11 Apr 2026 - 8:06

score 48 · Answer 10 · 2026-04-13 18:30:12

48

Views

(combinations) choosing 6 students from 8 boys and 7 girls with at least 2 boys and 2 girls

Published on 13 Apr 2026 - 18:30

score 87 · Answer 11 · 2026-04-13 04:17:02

Ways to distribute 15 distinct kinds of toys with at least 10 of each kind to 10 kids so that each kid gets at most one kind of each toy?

score 54 · Answer 12 · 2026-04-16 12:22:59

54

Views

Combinatorial doubt, why ${}^{n}C_{1}.{}^{(n-1)}C_{1}\neq {}^{n}C_2$

Published on 16 Apr 2026 - 12:22

score 131 · Answer 13 · 2026-04-09 23:29:14

131

Views

Help needed with my detailed analysis of 'mis-application of product principle'.

Published on 09 Apr 2026 - 23:29

score 97 · Answer 14 · 2026-04-12 10:47:04

97

Views

Is there a combinatorial proof of this recurrence relation for families of sets thus defined?

Published on 12 Apr 2026 - 10:47

score 124 · Answer 15 · 2026-05-02 14:46:39

124

Views

Equation $\frac{1}{a_1}+\ldots +\frac{1}{a_{2018}} = 1$

Published on 02 May 2026 - 14:46

List Question

How many strings of length $10$, with letters taken from $\{A, B, C, D, E\}$, contain at least $1$ $A$ and at least $1$ $B$?

Every graph $G$ with $d(G) \ge 4k$ has a $(k + 1)$-connected subgraph $H$ such that $\epsilon (H) > \epsilon(G) − k$.

Is the set of extensive, increasing, ∅-preserving operators 2^X→2^X closed under composition?

Analysis of super-structures emerging in a spiral representation of prime numbers

Recurrence Relation of Stirling number of second kind.

combinatorics: a variant of set covering/subset selection problem?

Digits of a number and the probability of product of the digits being even

$\sum_{j=1}^n \sum_{k=j+1}^n (1)$

How many exam papers earn a grade of $90%$

(combinations) choosing 6 students from 8 boys and 7 girls with at least 2 boys and 2 girls

Ways to distribute 15 distinct kinds of toys with at least 10 of each kind to 10 kids so that each kid gets at most one kind of each toy?

Combinatorial doubt, why ${}^{n}C_{1}.{}^{(n-1)}C_{1}\neq {}^{n}C_2$

Help needed with my detailed analysis of 'mis-application of product principle'.

Is there a combinatorial proof of this recurrence relation for families of sets thus defined?

Equation $\frac{1}{a_1}+\ldots +\frac{1}{a_{2018}} = 1$

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