Triangle "Missing Square" Puzzle

by profhankd, published

Triangle "Missing Square" Puzzle by profhankd Jun 22, 2014
0 Share
Download All Files

Thing Apps Enabled

Order This Printed View All Apps


Liked By

View All

Give a Shout Out

If you print this Thing and display it in public proudly give attribution by printing and displaying this tag.

Print Thing Tag

Thing Statistics

1494Views 344Downloads Found in Puzzles


You've probably seen this puzzle before. There are four pieces, in this version clearly marked with 1cm grid, which together are placed inside a simple base to form a triangle with a 1cm3 hole when assembled. However, if you put the pieces back in a different order, the hole disappears!

The hard part isn't putting the puzzle together, but figuring out: Where does the hole go?


An easy print. The version shown was printed with 20% fill in purple PLA on a MakerGear M2.

Where does the hole go?


You get a little hint as to what is happening by the fact that the pieces assembled into the base are a tight fit with the hole and have some play without the hole. In fact, the two triangles do not have the same slope, although they are close enough to look the same. The markings on the base and pieces are accurately placed at 1cm intervals, so you can confirm the slopes are different by counting grid units on the sides.

Normally, this puzzle isn't done with a base, so you don't have a straight edge to compare the bent edge with. However, the bend is small enough that it is not obvious even with the straight edge of the base to compare it against. Thus, the puzzle is made even less intuitive.

The space for the hole is really coming from having half a cube more or less of space in the gap between the parts and the base edges than you would expect by the base's apparent 5x13 dimensions. You don't notice that the base is actually slightly oversize because the grid markings have thickness, easily concealing the tiny amount of extra space needed around the edges. Naturally, in the hole-free configuration, the fit is less tight.

The moral of the puzzle, very appropriate for folks involved in 3D printing, is that tolerance issues too small to see can make a surprisingly significant and visible difference....

More from Puzzles

view more

All Apps

Auto-magically prepare your 3D models for 3D printing. A cloud based 3D models Preparing and Healing solution for 3D Printing, MakePrintable provides features for model repairing, wall thickness...

App Info Launch App

Kiri:Moto is an integrated cloud-based slicer and tool-path generator for 3D Printing, CAM / CNC and Laser cutting. *** 3D printing mode provides model slicing and GCode output using built-in...

App Info Launch App
KiriMoto Thing App

With 3D Slash, you can edit 3d models like a stonecutter. A unique interface: as fun as a building game! The perfect tool for non-designers and children to create in 3D.

App Info Launch App

Print through a distributed network of 3D printing enthusiasts from across the US, at a fraction of the cost of the competitors. We want to change the world for the better through technology, an...

App Info Launch App

Quickly Scale, Mirror or Cut your 3D Models

App Info Launch App

Treatstock is an online platform that offers decentralized manufacturing services such as 3D printing and CNC machining for business-to-business and business-to-consumer sales all over the world. W...

App Info Launch App

3D print your favourite design with NinjaPrototype, a professional 3D manufacture with consistent quality and speed.

App Info Launch App