**1) 3-7=8?**^{***/*****}

Please correct the following equation by moving two matchsticks:

You can check your solutions here

New puzzles are published at least twice a month on Fridays.

**1) 3-7=8?**^{***/*****}

Please correct the following equation by moving two matchsticks:

You can check your solutions here

New puzzles are published at least twice a month on Fridays.

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What do you read when you superposition these three figures?

You can check your solution here

New puzzles are published twice a month on Fridays. Solutions are revealed one or more weeks later.

This puzzle was inspired by the “100 doors” app, and by the Dutch translation of 1000 casse-tete et enigmas by Piere Berloquin.

Dominosas are puzzles where the dominoes have been shuffled and turned face up. All the numbers are given, but the borders between the dominoes are not given – these have to be solved by the reader.

I used to publish quarterly on them at my site domino plaza.

Usually a 6×6 set of dominoes is used, though larger or smaller sets can be used.

Here are two examples:

**1) The christmas bauble**^{**/*****}

You can check your solution here

**3) Solving strategies**

**a) Counts**

Make a count of how often all combinations appear. To do so, list all dominoes and how often they appear in the puzzle:

0-0: 2

1-0: 3

1-1: 5

2-0: 2

2-1: 1

2-2: 3

and so on.

This will give you the position of 2-1. Mark the borders on the printed puzzle.

**b) Cross off deleted connections**

Continuing the above example, it is easy to jump to a conclusion about 3-3, but before that we have some bookkeeping to do. Identifying the domino severed a number of links. In our example the severed links are the 3-1, 6-1, 2-0, and 5-2. When we update our list above for these severed links, we find that the number of 2-0 combinations is now reduced to 1, giving another domino.

**c) Unique positions.**

In this diagram, it is easy to see that in the top left position, only-the 3-3 is possible.

**d) Block impossible links**

Identifying the 3-3 domino blocks the link between all other 3-3 combinations:

This in turn, will in some situations trigger another situation like in step c)

New puzzles are published at least twice a month on Fridays. Solutions are usually published after one or more weeks.

External links:

https://www.puzzle-dominosa.com/ – play them online

https://www.chiark.greenend.org.uk/~sgtatham/puzzles/js/dominosa.html – another online game site

http://medmunds.github.io/puzzles/dominosa.html – 3rd in line play

https://play.google.com/store/apps/details?id=com.oxothuk.dominosa – android app

http://www.mathematica-journal.com/2014/10/three-ways-to-solve-domino-grids/ – three ways to solve them.

Last month we looked at some hexagon matchstick puzzles, and this month features some more.

**1) Move 4 matches**^{**/*****}

From the figure above, move 4 matchsticks so that you have 4 triangles on unequal size.

**2) Move 4 matches**^{***/*****}

From the figure above, move 4 matchsticks so that you have 6 triangles again.

You can check your solutions here and here.

New puzzles are published at least twice a month on Friday. Solutions are published after one or more weeks. You are welcome to remark on the difficulty level of the puzzles, discuss alternate solutions, and so on. Puzzles are rated on a scale of 1 to 5 stars.

Matchsticks puzzles are over a century old, but seem to go through a revival with several apps featuring them.

**1) Move 3 matches**^{**/*****}

From the figure above, move 3 matchsticks so that you have 4 same sized triangles.

**2) Move 4 matches**^{***/*****}

From the figure above, move 4 matchsticks so that you have 4 same sized triangles.

You can check your solutions here and here.

New puzzles are published at least twice a month on Friday. Solutions are published after one or more weeks. You are welcome to remark on the difficulty level of the puzzles, discuss alternate solutions, and so on. Puzzles are rated on a scale of 1 to 5 stars.

Have a look at the following figure:

You can easily check that 16 matches form 5 squares.

**Move 2 matches**^{**/*****}

Move 2 matches to create 4 squares

You can check your solution here

**Move 3 matches**^{**/*****}

Move 3 matches to create 4 squares

You can check your solution here

**Move 4 matches**^{**/*****}

Move 4 matches to create 4 squares

You can check your solution here

New puzzles are published at least twice a month on Friday. Solutions are published after one or more weeks. You are welcome to remark on the difficulty level of the puzzles, discuss alternate solutions, and so on. Puzzles are rated on a scale of 1 to 5 stars.

**3 triangles**^{***/*****}

Move 2 matchsticks to get 3 triangles:

You can check your solutions here.

**Surface**^{***/*****}

These 6 matches enclose an area with size 2 (2 standard triangles).

Rearrange them so that:

a) they enclose an area of exactly 4 triangles

b) they enclose an area of exactly 6 triangles

You can check your solutions here.

Recently I downloaded a couple of matchstick puzzle apps on my android phone and on my ipad. Below you find an incomplete list of android apps with matchstick puzzles.

Here is a short list:

Name | Publisher | Type of puzzles | Remarks |

Matchstick puzzle | Uysal Mehmet | Digital Puzzles | Minimalistic interface. It baffled me at first. I didn’t see hints or solutions, but that doesn’t mean they aren’t hidden somewhere. |

Puzzles with matches | Celtic Spear | Digital matches, triangles and squares | Well designed interface. Puzzles gradually increase in difficulty. Recommended! |

Matchstick puzzles | Gamophonica | Squares | At level 6, I found a symmetrical solution is not recognized. Interface is clear. Same on levels 7 & 8, and probably on subsequent levels too. I informed the publisher and they responded quickly to my email, so I trust this problem will be resolved when you read this (written dec 2016). |

Matches Puzzle Game | Bojan Klabjan | Squares, triangles, numerical digits | Original interface. Well designed. Recommended! |

Matchstick Puzzle | Alt-y | Digital numbers | Both moving and 1 and 2 matchsticks. |

Amazing matchsticks | Network Game&utility | ? | I skipped this one, as it asked 4 types of access which I deemed unnecessary |

Matches Puzzle 2016 | Fitapp Inc | Digital numbers | Both 1 and 2 matches to be moved. If you are stuck, solutions can be bought with in-game money. |

Math puzzle with sticks | LogiGames | Digital numbers | Beautiful interface, but I miss a clear indication of how many matches I have to move. Or maybe it is always just 1 match. |

I admit I’m not even halfway through the list.

Anyway, here are two puzzles.

**Problem 1**^{*/*****}

You can check your solutions here and here

**1) Move 6 matches**^{**}

Consider the following figure:

Now move 6 matches so that you have 4 squares.

You can check your solutions here

New puzzles are published at least twice a month on Fridays. Solutions are published after one or more weeks. You are welcome to remark on the difficulty level of the puzzles, discuss alternate solutions, and so on. Puzzles are rated on a scale of 1 to three stars.