# Cryptarithm: days

Days – 1**/*****

Days – 2****/*****

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.

# Matchstick – triangles

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.

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.

# Flags of countries (2)

Flags of countries (2)**/*****

Which of the following three flags belongs to the group above:

You can check your solutions 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.

# Cryptarithm: months

This time I present to you two cryptarithm: calculations in which every digit has been replaced by a letter.

Months 1****/*****

Months 2***/*****

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.

# Calcudocu / K-doku / Calcdoku

Calcdoku problems, also called K-doku or Calcudoku were invented in 2004 by Japanese math teacher Tetsuya Miyamoto, who intended the puzzles to be an instruction-free method of training the brain. He used the Japanese name KenKen, which could be translated as ‘Cleverness’. In his classes, he sets aside about 90 minutes each week for solving puzzles. He believe that when students are motivated, they learn better, and he lets them do so at their own pace.
Other names used for this type of puzzle are Kendoku and Kashikoku naru Puzzle. The names KenKen and Kenduko are trademarked. Books are in Japan published by Gakken Co. In the USA the New York Times started publishing them in 2008. In my native Netherlands they appear regularly in both puzzle magazines and general magazines.

A calcudoku puzzle consists of a latin square – a latin square can have any size. If its size 4, the numbers 1 to 4 should appear exactly once in every rown and column exactky once. Similarly, if its size 5, the numbers 1-5 should appears exactly once in every row and column.
The square is subdivided into smaller areas, and the sum, product, difference or division result is given in the top left corner.

Here are two example puzzles.
1) 4×4**/*****

You can check your solution here

2) 5×5**/*****

You can check your solution here

3) 6×6****/*****
is an example puzzle, kindly offered by Jacques Min, who runs a website specialized in Calcudoku puzzles: :

Techniques for solving them:
* http://www.conceptispuzzles.com/index.aspx?uri=puzzle/calcudoku/techniques
*

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.

# Takuzu / Binairo

Takuzu (often called Binairy/Binairo or occasionally Tic-Tac-Toe) puzzles have been around for several years. In my native Netherlands they have been published by both Sanders puzzles and by Denksport, and also in daily newspaper Algemeen Dagblad.
In France, they have been published under the name Takuzu in le Figaro, at least in 2011.

The puzzle consists of a rectangle or square with an even number of rows and columns. This is partly filled with 0’s and 1’s. It should be completed by the solver with 0’s and 1’s in such a way that:
a} There are never more than two consecutive 0’s or 1’s in any row or column;
b) There are an equal number of 0’s and 1’s in every row and column;
c) All rows and columns are different;
This last condition seems to be rarely used in the commercial publications. Sizes are usually 10×10, 12×12 or 14×14, though 6×6 and 8×8 are often offered as introduction puzzles.

Example 1:

puzzle 1: 6×6:***/*****

puzzle 2: 7×7:***/*****

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.

# Flags (1)

Flags of countries (1)***/*****
Look at these flags:

Which of the following three flags belongs in the above group:
a)

You can check your solutions 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.

# Cryptarithm

This weeks puzzle comes from “Quark special”, a Japanese puzzle booklet or magazine that I once obtained through the late Nob Yoshigahara.

You can check your solutions 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 three stars.

# Matchsticks – a list of apps

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*/*****

Problem 1***/*****

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.

# Ages

Ages**/*****

Ages**/*****
A man is 25 years old and his wife 23. He noticed that the sum of their ages (25+23=48) is exactly 4 times the sum of the digits of their ages. (2+5+2+3=12).

When will the sum of their ages be exactly 8 times the sum of the digits of their ages? And when will it be 9 times the sum of the digits?

You can check your solutions 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.