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In how many ways can $10$ letters be placed in $10$ addressed envelope such that exactly $9$ letters are in correct envelope?

score 1.5k · Answer 1 · 2026-04-15 22:32:49

1.5k

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In how many ways can $10$ letters be placed in $10$ addressed envelope such that exactly $9$ letters are in correct envelope?

Published on 15 Apr 2026 - 22:32

score 26.4k · Answer 2 · 2026-04-14 01:33:58

26.4k

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Finding the n-th lexicographic permutation of a string

Published on 14 Apr 2026 - 1:33

score 4.8k · Answer 3 · 2026-04-16 03:05:49

4.8k

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$x=\frac{-b\pm \sqrt{b^2-4ac}}{2a}$ show that $x=-c/b$ when $a=0$

Published on 16 Apr 2026 - 3:05

score 4.5k · Answer 4 · 2026-04-24 03:46:10

4.5k

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Ten soldiers puzzle

Published on 24 Apr 2026 - 3:46

score 434 · Answer 5 · 2026-04-26 07:52:11

434

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Expressing any given number in the form of $x^y + y^x$

Published on 26 Apr 2026 - 7:52

score 3k · Answer 6 · 2026-05-02 02:48:35

3k

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Triangle whose height and sides are consecutive integers

Published on 02 May 2026 - 2:48

score 442 · Answer 7 · 2026-04-17 14:28:15

442

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One drunk receptionist and four brilliant mathematicians

Published on 17 Apr 2026 - 14:28

score 10k · Answer 8 · 2026-04-11 13:19:46

10k

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Expanding and understanding the poison pills riddle

Published on 11 Apr 2026 - 13:19

score 315 · Answer 9 · 2026-04-14 10:07:55

315

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What is the area of triangle AFE?

Published on 14 Apr 2026 - 10:07

score 3.5k · Answer 10 · 2026-04-11 04:22:13

3.5k

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A variant of the Monty Hall problem

Published on 11 Apr 2026 - 4:22

score 224 · Answer 11 · 2026-04-14 10:11:18

224

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What is the ratio of the area?

Published on 14 Apr 2026 - 10:11

score 3.4k · Answer 12 · 2026-04-15 12:50:05

3.4k

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4 items add up to and multiply to 7.11 what are the value of the items?

Published on 15 Apr 2026 - 12:50

score 238 · Answer 13 · 2026-04-14 11:35:45

238

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Determining the round players will meet in a knock-out tournament

Published on 14 Apr 2026 - 11:35

score 222 · Answer 14 · 2026-04-16 13:28:31

222

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Puzzle: Can you find an elementary proof that every $n \gt 6$ can be represented as a sum of $O(\log n)$ distinct primes?

Published on 16 Apr 2026 - 13:28

score 505 · Answer 15 · 2026-04-15 14:02:21

505

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Puzzle: Can arithmetic be axiomatized with a single two-term relation?

Published on 15 Apr 2026 - 14:02

List Question

In how many ways can $10$ letters be placed in $10$ addressed envelope such that exactly $9$ letters are in correct envelope?

Finding the n-th lexicographic permutation of a string

$x=\frac{-b\pm \sqrt{b^2-4ac}}{2a}$ show that $x=-c/b$ when $a=0$

Ten soldiers puzzle

Expressing any given number in the form of $x^y + y^x$

Triangle whose height and sides are consecutive integers

One drunk receptionist and four brilliant mathematicians

Expanding and understanding the poison pills riddle

What is the area of triangle AFE?

A variant of the Monty Hall problem

What is the ratio of the area?

4 items add up to and multiply to 7.11 what are the value of the items?

Determining the round players will meet in a knock-out tournament

Puzzle: Can you find an elementary proof that every $n \gt 6$ can be represented as a sum of $O(\log n)$ distinct primes?

Puzzle: Can arithmetic be axiomatized with a single two-term relation?

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