Question

Problem proving $ P_{r}^{r} + P_{r}^{r+1} + ... + P_{r}^{2r} = P_{r}^{2r+1} $

score 95 · Answer 1 · 2014-09-21 05:00:53

95

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Problem proving $ P_{r}^{r} + P_{r}^{r+1} + ... + P_{r}^{2r} = P_{r}^{2r+1} $

Published on 21 Sep 2014 - 5:00

score 8.2k · Answer 2 · 2026-03-30 12:43:43

8.2k

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How many words can be formed by taking 4 letters at a time from the letters of the word 'MORADABAD'?

Published on 30 Mar 2026 - 12:43

score 75 · Answer 3 · 2014-09-21 16:02:07

75

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number of rectangles (including squares)

Published on 21 Sep 2014 - 16:02

score 675 · Answer 4 · 2014-09-21 23:36:55

675

Views

Probability of being selected twice in a week given a set of n people?

Published on 21 Sep 2014 - 23:36

score 19.2k · Answer 5 · 2026-04-08 20:53:24

19.2k

Views

Permutation & combination for creating housie tickets

Published on 08 Apr 2026 - 20:53

score 1.5k · Answer 6 · 2014-09-22 13:47:04

1.5k

Views

Problem finding the number of r-element multi-subsets of the multi-set $M=\{ a_{1},a_{2},...,a_{n},m.b \} $

Published on 22 Sep 2014 - 13:47

score 61 · Answer 7 · 2014-09-22 15:34:42

61

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Proving $ \sum_{r=0}^{n} \frac{1}{r+1} \binom{n}{r} = \frac{1}{n+1} (2^{n+1} - 1) $

Published on 22 Sep 2014 - 15:34

score 1.2k · Answer 8 · 2014-09-23 06:40:39

1.2k

Views

How many ways can we put $5$ red balls, $4$ green balls and $3$ white balls into $12$ slots?

Published on 23 Sep 2014 - 6:40

score 2.2k · Answer 9 · 2014-09-23 07:33:19

2.2k

Views

How many hands are there with exactly 5 hearts after drawing 7 cards from a deck?

Published on 23 Sep 2014 - 7:33

score 562 · Answer 10 · 2026-03-27 23:31:52

562

Views

View a group acting faithfully and transitively on a set $X$ as a subgroup of a wreath product.

Published on 27 Mar 2026 - 23:31

score 107 · Answer 11 · 2026-04-12 23:35:06

107

Views

Indexing ranked permutations into other ranked permutations

Published on 12 Apr 2026 - 23:35

score 1.8k · Answer 12 · 2014-09-24 16:43:15

1.8k

Views

Number of ways to schedule activities using combination or permutation.

Published on 24 Sep 2014 - 16:43

score 21k · Answer 13 · 2014-09-24 16:57:30

21k

Views

Why does the wording of how many ways can a photographer 6 people from a group of 10 ask for permutations and not combinations?

Published on 24 Sep 2014 - 16:57

score 72 · Answer 14 · 2026-04-12 04:04:04

72

Views

Probability of a number of weighted items being allocated to the same bin

Published on 12 Apr 2026 - 4:04

score 136 · Answer 15 · 2026-04-12 09:23:05

136

Views

Combinations and Permutations: Number of ways of taking out 1 $ bills

Published on 12 Apr 2026 - 9:23

List Question

Problem proving $ P_{r}^{r} + P_{r}^{r+1} + ... + P_{r}^{2r} = P_{r}^{2r+1} $

How many words can be formed by taking 4 letters at a time from the letters of the word 'MORADABAD'?

number of rectangles (including squares)

Probability of being selected twice in a week given a set of n people?

Permutation & combination for creating housie tickets

Problem finding the number of r-element multi-subsets of the multi-set $M=\{ a_{1},a_{2},...,a_{n},m.b \} $

Proving $ \sum_{r=0}^{n} \frac{1}{r+1} \binom{n}{r} = \frac{1}{n+1} (2^{n+1} - 1) $

How many ways can we put $5$ red balls, $4$ green balls and $3$ white balls into $12$ slots?

How many hands are there with exactly 5 hearts after drawing 7 cards from a deck?

View a group acting faithfully and transitively on a set $X$ as a subgroup of a wreath product.

Indexing ranked permutations into other ranked permutations

Number of ways to schedule activities using combination or permutation.

Why does the wording of how many ways can a photographer 6 people from a group of 10 ask for permutations and not combinations?

Probability of a number of weighted items being allocated to the same bin

Combinations and Permutations: Number of ways of taking out 1 $ bills

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