supercat
  • Member for 7 years, 6 months
  • Last seen more than a week ago
  • Illinois
3 answers
14 votes
2k views
Touching Matchsticks
11 votes

An arrangement which can be readily seen to be valid albeit not minimal may be formed by observing that joining two "small" (3-matchstick) triangles and two "large" (9-matchstick) rigid triangles will ...

View answer
15 answers
50 votes
7k views
Find the identity of the four troll brothers
10 votes

I believe four works. Figure that at some point one will ask Zrowag a question and get no response, so that burns a question but the only relevant permutations are the six involving the other ...

View answer
4 answers
53 votes
6k views
Is this chromatic puzzle always solvable?
10 votes

. .

View answer
6 answers
16 votes
2k views
180 degree rotation matchstick equality
10 votes

What answer is "best" depends on how one defines "trivial", but if the goal is to have an answer which uses different arithmetical relationships when inverted, how about 21-9 ...

View answer
5 answers
27 votes
9k views
Is there a proof that a map of the United States requires 4 colors?
10 votes

That four colors will suffice may be easily shown by the fact that four-color maps exist. That three colors will not suffice may readily be shown by pointing out particular places where it is ...

View answer
9 answers
7 votes
1k views
Five beautiful ladies
9 votes

A nasty thing about liars is that when asked complex questions, they may answer in whatever fashion, other than 100% truthfulness, would be most vexing. That is a substantial complication which other ...

View answer
4 answers
5 votes
255 views
What is the minimum High Card Points needed for a partnership to be able to claim all 13 tricks in Bridge?
8 votes

7S can be forcibly won with five HCP: . ♠8765432/-/♦765432/- ♠K/♥AK/♦AKQJ/♣AKQJT9 ♠Q/♥QJ/♦T98/♣8765432 . ♠AJT9/♥T98765432/-/- If West ...

View answer
3 answers
14 votes
1k views
No moves at all, not even to put yourself in check
8 votes

How about I think that's an alternative 6+1-piece solution.

View answer
4 answers
11 votes
1k views
Pop the Last Balloon
6 votes

For the general case of N balloons, if it's not possible to pop all the balloons, a winning move is... If that move is unavailable... To understand why this is so... Conversely...

View answer
3 answers
3 votes
669 views
Monopoly Game Show: Is there a winning strategy?
Accepted answer
6 votes

If passenger counts from 1 to 5 are equally distributed, it's possible to compute for each of the 343 (7x7x7) possible population distributions the expected value if one stands pat and if one takes ...

View answer
7 answers
49 votes
8k views
The Circular Prison of Unknown Size
5 votes

The task may be established, in a huge but bounded number of moves, by first establishing an upper bound M on the number of prisoners (possibly using Julian Rosen's approach) and repeatedly performing ...

View answer
9 answers
5 votes
1k views
Robot Long and Robot High
Accepted answer
4 votes

I would guess the intended answer is that... A potentially safer approach would be...

View answer
3 answers
40 votes
4k views
The "M&M Sugar Rush" game
4 votes

If there are six candies on the table, the expected number of additional candies to eat will be zero. If there are five on the table, the expected number will be 5/6 of (two plus whatever the ...

View answer
3 answers
17 votes
3k views
Can I Haz My Eye Center'd?
3 votes

If curved cuts are not permitted, it may be possible, depending upon the size and placement of the cat, to cut a regular polygon which is entirely within the circle but outside the cat, such that ...

View answer
4 answers
13 votes
1k views
Rewritable punch cards
3 votes

An adaptation of r's approach, if the requirement is to, for any k, find a B such that N bits of storage can be used to allow kN/B distinct writes, is to pick B=3k, and encode the information as ...

View answer
2 answers
5 votes
598 views
The Unknown Prison of Unknown Size
3 votes

If there is no known maximum number of switches and bulbs, the first part of the solution (finding a known upper bound) becomes much harder (refer to the other puzzle for the approach that's workable ...

View answer
5 answers
21 votes
5k views
People trapped in a shrinking room
3 votes

A limitation of the solution given by eclipz905 is that portions of the walls would be moving away from the center. An alternative approach would be to have walls of a flexible or articulated ...

View answer
3 answers
6 votes
930 views
How would one make a good liars puzzle?
2 votes

To my mind, puzzles where the goal is to formulate questions are more interesting than those which merely require finding a distribution of liars and truth-tellers that satisfies a given set of ...

View answer
24 answers
87 votes
24k views
How do you prove that mirrors aren't parallel universes?
2 votes

How about a concave mirror, like some of the ones found in cosmetic or vanity kits? Unless one wanted to speculate that such a mirror provides views into an infinite multitude of universes that just ...

View answer
5 answers
10 votes
951 views
Help me improve the jumping robot problem
2 votes

If both sides of the gorge are at the same elevation, and if the rabbit and bear collide in the middle, the rabbit's effect on the bear's momentum will be worse than if the rabbit had simply been ...

View answer
12 answers
74 votes
13k views
Turn off all lights in a ring-shaped palace
2 votes

As Tanner Swett has noted, it's possible to solve the puzzle using a finite number of states beyond those of the lights themselves. His solution takes time proportional to the square of the number of ...

View answer
17 answers
40 votes
6k views
XKCD inspired logic puzzle
1 votes

Assuming the doors are numbered 1, 2, and 3, ask the guard in front of door #2, "Is the sum of the number on the liar's door and the number on the door that leads to death, even". If the answer is "...

View answer
11 answers
18 votes
2k views
Little Lost Robot
1 votes

Order each robot to push a button that new robots know nothing about, but that the "get lost" robot would recognize as causing a door to slam on one's toe in a manner that would be slightly, though ...

View answer
5 answers
7 votes
826 views
Highest possible score my friend could earn in one Scrabble turn?
1 votes

If one is playing against an exceptionally cooperative opponent who never challenges any words, no matter how outrageous, I think the maximum would be 2449 when playing against a single opponent. ...

View answer
6 answers
2 votes
252 views
Phrase for _CY_E
1 votes

Instructing someone to freeze ('icy be'), or saying one is frozen ("Icy me")? If the puzzle is using cryptics, perhaps an abbreviated institution got mixed up with a yes-man (ACYOE interleaves "CO" ...

View answer
7 answers
49 votes
8k views
The Circular Prison of Unknown Size
1 votes

Once a bound on the number of prisoners is established, the problem may be solved in polynomial time (rather than hyper-exponential) without requiring prisoners to use an overly-complicated rule sheet,...

View answer
4 answers
7 votes
646 views
Paint the rectangle with least movement
1 votes

A solution much better than Penguino's "spiral" can be achieved by starting with Penguino's zig-zag (the one with length 5098) but adjusting it slightly. Looking at the first place the line comes ...

View answer
4 answers
8 votes
1k views
Social Engineering (The Birthrate Problem)
1 votes

If the sex of each child is independently randomly determined with a 2:1 ratio favoring boys, then the stated policy will have no effect on male versus female birth rates. If, however, the events are ...

View answer
5 answers
9 votes
4k views
A rope-cutting problem
1 votes

An approach which would be much more dangerous, but would be usable even if there were only one rope would to climb each rope (or the rope) and slice partway through it while leaving it strong enough ...

View answer
4 answers
3 votes
461 views
Classic 2 Guards But With 3 Doors Instead
0 votes

If the lying guard is guaranteed to be "maximally" untruthful, and the doors are labeled 1, 2, and 3, one could ask a guard to identify every number between 1 and 6, inclusive, which either identifies ...

View answer