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Welcome to perplexus.info, flooble's perplexing puzzle portal. Here, we collect all sorts of puzzles, from simple logic questions and word tricks to in-depth math problems like probability and geometry. Click around and see if your brain is up to the task! If you're new here, make sure you sign up so that you can leave comments and submit your own problems!
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Difficulty: 4 of 5 Latest: 3D geometry (in Shapes)
PABCDE is a pyramid with ABCDE a convex pentagon. A plane meets the edges PA, PB, PC, PD, PE in points A', B', C', D', E' distinct from A, B, C, D, E and P. For each of the quadrilaterals ABB'A', BCC'B, CDD'C', DEE'D', EAA'E' take the intersection of the diagonals. Show that the five intersections are coplanar.
(No Solution Yet, 0 Comments) Submitted on 2021-01-22 by Danish Ahmed Khan   
Difficulty: 3 of 5 Bonus: It is infinite if it isn't? (in Paradoxes) Rating: 3.00
Most two person games are finite; for example, chess has rules that don't allow an infinite game, and tic-tac-toe obviously ends after at most 9 plays.

Let's define a new two person game: the "Metagame". The first player first picks any two person finite game (e.g., chess or tic-tac-toe). Then, the second player sets up the board (or whatever is needed) and makes the first move in that game, and the Metagame winner will be whoever wins that game.

The question: is Metagame finite or infinite?

(Solution Posted, 35 Comments) Submitted on 2005-04-12 by Old Original Oskar!   
Difficulty: 3 of 5Giant divisibility (in Just Math)
Posted on 2021-01-21 by Danish Ahmed Khan (No Solution Yet, 2 Comments)
Difficulty: 3 of 5Complex hexagon ratios (in Just Math)
Posted on 2021-01-20 by Danish Ahmed Khan (No Solution Yet, 2 Comments)
Difficulty: 3 of 5A tinted train (in Logic)
Posted on 2021-01-19 by Ady TZIDON (No Solution Yet, 1 Comments)
Difficulty: 3 of 5Sweet little sixteen (in Just Math)
Posted on 2021-01-18 by broll (No Solution Yet, 1 Comments)
Difficulty: 2 of 5Colinearity with rectangle vertex (in Geometry)
Posted on 2021-01-17 by Danish Ahmed Khan (No Solution Yet, 0 Comments)
Difficulty: 3 of 53 to 6 letters (in Word Problems)
Posted on 2021-01-16 by Ady TZIDON (No Solution Yet, 7 Comments)
Difficulty: 3 of 5Reverse engineering (in Tricks) Rating: 3.00
Posted on 2021-01-15 by Ady TZIDON (No Solution Yet, 1 Comments)
Difficulty: 3 of 5Literary apparel (in Word Problems) Rating: 5.00
Posted on 2021-01-14 by Math Man (No Solution Yet, 2 Comments)
Difficulty: 4 of 5number sum equals all digit sum (in Numbers)
Posted on 2021-01-13 by Danish Ahmed Khan (No Solution Yet, 2 Comments)
Difficulty: 3 of 5Solitaire: Probability Of No First Move (in Probability)
Posted on 2021-01-12 by Larry (No Solution Yet, 3 Comments)
Difficulty: 2 of 5Salt (in Word Problems) Rating: 4.67
Posted on 2021-01-11 by Charlie (Solution Posted, 2 Comments)
Difficulty: 4 of 5Lattices inside square (in Just Math)
Posted on 2021-01-10 by Danish Ahmed Khan (No Solution Yet, 0 Comments)
Difficulty: 3 of 5Go one, two, three (in Numbers) Rating: 3.00
Posted on 2021-01-09 by Danish Ahmed Khan (No Solution Yet, 6 Comments)
Difficulty: 3 of 51 2 4 8 (in General)
Posted on 2021-01-08 by Ady TZIDON (No Solution Yet, 2 Comments)

Recently Posted Solutions:
Difficulty: 2 of 5Salt (in Word Problems)
Submitted By Charlie. Solution posted on 2021-01-14 21:51:53
Difficulty: 3 of 5A's, B's, C's and D's 4 (in Logic)
Submitted By Charlie. Solution posted on 2021-01-14 21:51:03
Difficulty: 4 of 5Not The Weakest Link (in Probability)
Submitted By Charlie. Solution posted on 2020-12-31 07:31:27
Difficulty: 4 of 5Five numbers and Six sums (in Numbers)
Submitted By Brian Smith. Solution posted on 2020-12-23 16:03:58
Difficulty: 2 of 5The King Shows Some Mercy (in Probability)
Submitted By Charlie. Solution posted on 2020-12-22 10:29:37
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