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Questions tagged [geometry]

A puzzle related to shapes, geometric objects (polygons, circles, solids, etc.) of any number of dimensions, relative position of figures, and the properties of space.

1
vote
2answers
152 views

Is this six different views of the same block or is there a consistent view with 1 or more that is 'odd'

The answer book of this puzzle book says that the first five are all consistent but the last one is not because the Z has to be a U. I can't seem to agree with this as U seems to be attached to N, P, ...
7
votes
1answer
546 views

How many different pentagons in this grid? [duplicate]

The 3x3 grid is given as below; How many pentagons could be drawn by connecting the dots by lines in the grid? Rules: Pentagons could be convex or concave. The lines cannot intersect each other. ...
4
votes
1answer
975 views

The Four Coins Puzzle [duplicate]

Four coins lie on a table and form a square. Now you are allowed to jump with a coin over another one, in any direction, i.e. also diagonally or however. You always have to jump all the way to the ...
4
votes
2answers
207 views

Three-dimensional snooker

Bert practises potting snooker balls on an elliptical table. He places a ball at one focus, strikes it with his cue in a random direction so that it travels towards the edge of the table, and when it ...
0
votes
1answer
366 views

Dissecting a triangle into 4 pieces [closed]

How can I dissect a triangle into 4 piece and form a square? I took A right triangle with sides 3,4,5.i was able to get a rectangle of side 3 and 2,if I dissect that I was able to get 3 squares of ...
7
votes
3answers
317 views

A different cyclicity condition

Note: Although this may seem maths-related, I did do some research on meta and it seems that questions which take an 'elegant' solution are on-topic. There are many ways to tell if four points are ...
7
votes
2answers
484 views

Overlapping Tiles

Suppose you had two stained-glass tiles in the shapes of polygons and you laid them on top of each other. Their overlapping area also forms a polygon, like the ones I have shown in the image: Notice ...
4
votes
1answer
900 views

How many boxes do you see?

My professor gave us this puzzle at the beginning of the semester but would not reveal the answer: There is only one question: How many boxes do you see? We were not given any other information and ...
10
votes
2answers
773 views

6 Points in a rectangle

Here is an (unoriginal) question which I found quite nice. I've got no idea where the original question came from. Given 6 points in a $3\times4$ rectangle, prove that two lie within $\sqrt{5}$ of ...
7
votes
2answers
1k views

Is there a simple algorithm for solving Kami 2 puzzles?

I'm finding my life has been consumed by Kami 2, partly because I seem to have achieved some "insight" and am able to solve the puzzles reliably, almost always on the first try. The rules are simple: ...
15
votes
2answers
693 views

Ernie and the Optical Gyroscopes

I almost always take up Ernie’s offers to crew on his boat, when he suggests an overnight expedition. But when he phoned last Thursday I had to remind him that it was TV night, and Acme Satellite ...
5
votes
1answer
186 views

Cover 3*2.6 rectangle with the least number convex polygons cut from sheets of given size 1.2*2.4

I want to cover a rectangle of given dimensions ($3\times2.6$) with a minimal number of convex polygons cut from rectangular sheets of material of given size ($1.2\times2.4$). These polygons don't ...
12
votes
3answers
321 views

Who let the dogs off?

Four people, A, B, C, and D brought their dogs to a square park, 1 (mile/km) on each side. They stood at the four corners. Suddenly all four dogs broke free from their lea(shes/ds) at once. A ran at ...
4
votes
2answers
1k views

Can you divide this figure into two equal parts? [duplicate]

This is very simple when I see the answer, but I was not able to answer it(by thinking of single line), So posting for you.
7
votes
5answers
708 views

One a puzzle, two a puzzle, Hot Cross Clocks

It's Good Friday! I want to make perfect hot cross buns by superimposing two 12-hour clock faces on top of each other. Is this possible, and if so, how many ways are there of doing so? In other ...
1
vote
1answer
401 views

Mr. Allen at the Mall

Mr. Woody Allen is standing at one of the three entrances (A) of a 5 story Manhattan Mall. He needs to go from A to the other end (small shop) on the 4th floor at location (X). Ground floor is First ...
7
votes
8answers
1k views

Thinking of a shape

This is on a similar thought process as a 2 year old puzzle on this site: You have one question to tell whether the number I'm thinking of is 1, 2, or 3 I am thinking of a shape. It is ...
11
votes
2answers
1k views

Which tile completes the set?

This one puzzles me. I hope you can solve it.
-2
votes
1answer
193 views

Conveyor belt brain teaser [closed]

Okay folks, I'm keen to get a response to this brain teaser!!! Let's say you're looking at a conveyor belt... The width = 2m, and the length = 10m. Okay... This conveyor belt is moving from right ...
6
votes
2answers
807 views

Building a pyramid from di-spheres

Suppose you want to build a square pyramid made up of 30 spheres. So the bottom layer is a 4x4 square arrangement of touching spheres, and it has 3x3, 2x2 and 1x1 layers on top. The building blocks ...
27
votes
5answers
702 views

Dissecting the holey octomino into a square

This is a pure dissection problem, with no added twists. Cut the holey octomino (i.e., a square with the middle third removed) into several pieces, and reassemble those pieces into a square with no ...
1
vote
2answers
274 views

Can you mark the SPOTS?

You are in a room which is 300 wide x 300 long x 300 tall in cm. Your job is to mark a couple of spots on one of the (non-window) walls. Spot 1: about 73 cm high on the side of the wall (x and y ...
2
votes
1answer
149 views

Brother Trouble [closed]

Three Brothers Decided to purchase circular land(marked in red) if the price of entire Circular land(circle P) = $29670 How Much They have to pay for the land marked in RED ?? Useful information: 1)...
6
votes
6answers
1k views

Circular geometry puzzle [closed]

Look at the images and pick the first one, then prove that the blue area = the white area here's my failed attempt: let radius of large circle = 1, so radius of small circle = 0.5 and length of ...
2
votes
1answer
509 views

Eight identical spheres fit inside a cube

Eight identical spheres fit inside a cube with side length of 1 unit. What is the largest possible radius for a sphere which would fit between those 8 spheres (in the center)? There are no gaps ...
5
votes
1answer
470 views

Make a tetrahedral pyramid with these puzzle pieces.

Recently on a local fair (mela) I bought this puzzle from a magic-stall. It contains the following parts (each part is rigid, inflexible) Fig- 1 : Dismantled pieces in 1 set. It contains : ...
7
votes
1answer
417 views

Can you arrange 36 trees so that there are 9 rows of 8 trees?

How could you arrange 36 trees into 9 rows of 8? (Note that a row is a straight line that can go in any direction.)
6
votes
5answers
1k views

Find the side view and simple 3d [closed]

Find the side view and simple 3d associated with these views.It is given that there are no hidden lines (lines which are not visible from the side or top view).
33
votes
7answers
2k views

Create a 3 inch measurement

How will you create a 3 inch (within say plus or minus 0.05 inch) side on a standard piece of paper ( 8.5 x 11 inches) merely by Folding? No marking of any kind allowed. Only one paper available. ...
3
votes
1answer
452 views

Infinitely simple polygon solipsism

           Solipsism — The self is all that can be known to exist. Above is a simple polygonal region divided into infinitely many different-...
9
votes
3answers
362 views

Unreflected infinitely simple polygon reflexivity

(This was retrofitted to more tightly match a surprise solution and to allow for another puzzle with the original intent.)                   &...
21
votes
3answers
3k views

Find 77777 solutions

You have three flat pieces, as shown: Arrange them flat, without overlap, such that the shape formed by the black parts is congruent to the shape formed by the white parts. Rotation and reflection ...
31
votes
6answers
3k views

Find 7 solutions

You have three flat pieces, as shown: Arrange them flat, without overlap, such that the shape formed by the black parts is congruent to the shape formed by the white parts. Rotation and reflection ...
2
votes
1answer
155 views

Connect three rings

Is it possible to arrange three rings so that they are connected and cannot be separated without cutting one, but once any one of the rings has been cut, the remaining two can be separated without ...
10
votes
1answer
537 views

Another dissection puzzle

The figure shows a hexagon and triangle tiled by six tiles, which are pairwise congruent. My question is: What is the smallest number of polygonal tiles that will tile both a regular hexagon and an ...
11
votes
5answers
820 views

My roommate is back add it!

My roommate's computer desk has a paper on it with these 3 weird grids and drawings. I know that he is trying to learn to write computer code and he likes making old video games as a way to learn. I'...
16
votes
4answers
932 views

Universal dissection

Alice has a squared paper 8 by 8. She cuts out one 1x1 square from it, at row N, column M. Bob cuts the rest of the paper into pieces. Once he is done, Alice asks Bob to put the pieces together in a ...
6
votes
3answers
279 views

2 circle with different radii covers same path on same number of turns… crack the fallacy

I found this puzzle from an old issue of a science magazine জ্ঞান ও বিজ্ঞান ("Knowledge and Science")(August, 1977); submitted by Amal Dash, a teacher of Scottish Church school, Kolkata; as mentioned ...
12
votes
1answer
266 views

Personally Attacked by Squares in a Bathroom

Well, this is a bit of a mess! Your bathroom has a rectangular floorspace of size $xn$ by $yn$, where $x, y, n$ are all positive integers, and now that you've removed those ghastly yellow and purple ...
7
votes
1answer
428 views

Character Navigation

Consider the following grid of streets with roadblocks: If you are facing in the direction of the arrow and want to get to the dot, the highlighted path is the shortest: This traces out an L. Let'...
11
votes
2answers
752 views

What the L are they trying to prove?

Seems some L t rominoes have developed a punk attitude and feel they have something to prove because people always play with dominoes instead.   They are even jealous of I trominoes, who ...
10
votes
2answers
305 views

Adventure of LALO : Open the Stargate Portal

While exploring a remote island under the project "Search for Knowledge Program", Archaeologist "LALO" has found a hidden stargate which will open a portal to the Knowledge Dimension. In order to ...
21
votes
1answer
505 views

From zero to parabola in 14 symbols

Post up, weekend analytic geometers, get ready to race for the parabola and approach the starting line with 0 and 7 other symbols:       0   =   ( ...
-6
votes
1answer
178 views

Find the radius

Information : AB = 8 CD = 7 O,B,D are centers of the respective circles Hint: Find hidden information/clue from the diagram to solve the puzzle. Note: diagram is not to scale; it is just for visual ...
-7
votes
5answers
226 views

Find The Radius Of All The Circles

Find the diameters of all the circles shown, given the information provided in the diagram below. All diameters are of integer length. P.S: the signature in the bottom right is mine and I own this.
15
votes
2answers
629 views

Ernie and the Slow Glass Solution

"Have a look at this" said Ernie when he dropped in unannounced yesterday, pulling what looked like an old-fashioned photographic negative from an envelope. I held the small plastic square up to the ...
8
votes
3answers
376 views

Find a straight tunnel 2

You have the same plugging task as in Find a straight tunnel , but now the problem requires a bit more imagination: Bob has a field, which is a regular polygon with $N$ sides and perimeter $P$. ...
17
votes
2answers
373 views

Santa's Sacks and the Puzzling Presents

It's that time of the year*, and Santa is delivering presents to all the good children of the world. *Almost, since the fortnightly challenge is a tad late :) Informed by his elves that his sacks ...
13
votes
1answer
335 views

Four Birds + One

You have a 7x7 tray, and several pieces as shown (the dimensions should be fairly obvious since the picture is to scale, but if not, a yellow bird piece fits snugly in a 4x4 square, the blue piece is ...
17
votes
3answers
298 views

Pairs of Pairs of Pentominoes

Split the 12 pentominoes into three sets of four. Can you pair up pentominoes so that each set makes two of the same shape? For instance, one of your three sets could look like this: That uses the L,...