Puzzle #8 The sum of the points of the dominoes in this square is 20. Find all the squares similar to this one where the sum of the points of the dominoes is 12. Note that the touching ends must match. Solut…

Solution

Four dominoes forming a square, each one with the number of spots, clockwise direction: two and three, three and one, one and four, and four and two. The number twenty is inside the square.

Puzzle #8
The sum of the points of the dominoes in this square is 20.
Find all the squares similar to this one where the sum of the points of the dominoes is 12.
Note that the touching ends must match.
Check the solution in the comments.
#math #logic #puzzle

Puzzle #7 Find the fourth domino in the sequence. Solution Note: For each term of the sequence, turn the domino 180 degrees and add 1 point in one side then subtract the points of the last term for the other…

Solution

Four dominoes, each one with the number of spots, from left to right, from top to bottom: six and one, two and five, three and three, and question mark and question mark.

Puzzle #7
Find the fourth domino in the sequence.
Check the solution in the comments.
#math #logic #puzzle

Puzzle #6 Three circles are inside of a big circle. The second circle and the third circle meet at the center/centre of the big circle. What fraction of the big circle is colored? Solution As the red circle …

Solution

Three stacked circles with different radii are inside a big circle, all tangent with each other. In the top it is the small circle, labeled/labelled pi. The medium circle is between the small circle and the bigger circle, it passes through the center/centre of the big circle and it is labeled/labelled four pi. The bigger circle is below the medium circle and it passes also through the center/centre of the big circle.

Puzzle #6
Three circles are inside of a big circle. The second circle and the third circle meet at the center/centre of the big circle.
What fraction of the big circle is colored?
Check the solution in the comments.
#math #geometry #puzzle

Puzzle #5 Two squares meet at the center/centre of a circle. The yellow square has area 20. What is the area of the red square? This puzzle was published on The Guardian. Solution Let r be the radius of the …

Solution

Two squares, one red and the other yellow, meet at the center/centre of a circle. The red square is smaller than the yellow square. The yellow square is labeled/labelled twenty.

Puzzle #5
Two squares meet at the center/centre of a circle. The yellow square has area 20.
What is the area of the red square?
This puzzle was published on @theguardian.com.
Check the solution in the comments.
#math #geometry #puzzle

Puzzle #4 The area of the isosceles triangle is 108. The dots separe the sides in equal parts. What is the area of the kite? Solution Let b and h be the base and the height of the isosceles triangle, respect…

Solution

An isosceles triangle where the base is divided into two equal parts by a dot and the two equal sides are divided into three equal parts by two dots. A green kite is inside the triangle where the top vertex coincides with the vertex of the triangle and the other vertices are the two top dots of the equal sides and the dot in the base of the triangle.

Puzzle #4
The area of the isosceles triangle is 108. The dots separe the sides in equal parts.
What is the area of the kite?
Check the solution in the comments.
#math #geometry #puzzle

Puzzle #3 The figure is created out of twelve matchsticks. Modify the position of four matchsticks to get two squares. Solution

Solution

A big square divided into four congruent small squares made with twelve matchsticks.

Puzzle #3
The figure is created out of twelve matchsticks.
Modify the position of four matchsticks to get two squares.
Check the solutions in the comments.
#math #matchstick #puzzle

Puzzle #2 The number 403 is created out of fifteen matchsticks. Modify the position of two matchsticks to get a number divisible by 9. This puzzle was published on The New York Times and on The Guardian. Sol…

Solution

The number four hundred three made with fifteen matchsticks.

Puzzle #2
The number 403 is created out of fifteen matchsticks.
Modify the position of two matchsticks to get a number divisible by 9.
This puzzle was published on @nytimes.com and on @theguardian.com.
Check the solution in the comments.
#math #matchstick #puzzle

Puzzle #1 The isosceles trapezoid/trapezium is composed of seven matchsticks. Modify the position of three matchsticks to get two equilateral triangles. This puzzle was published on NCTM and on The Guardian.…

Solution

Trapezoid/trapezium made with seven matchsticks.

Puzzle #1
The isosceles trapezoid/trapezium is composed of seven matchsticks.
Modify the position of three matchsticks to get two equilateral triangles.
This puzzle was published on @nctm.org and on @theguardian.com.
Check the solution in the comments.
#math #matchstick #puzzle

Mastering Geometry Puzzles (AK Peters/CRC Recreational Mathematics Series) Amazon.com: Mastering Geometry Puzzles (AK Peters/CRC Recreational Mathematics Series): 9781041245865: Ferro, Paulo: Books

(9/9)
You can pre-order it on Amazon (www.amazon.com/Mastering-Ge...) or any bookstore around the World. There are paperback, hardcover and Kindle versions available.

(8/9)
All the puzzles have step-by-step solutions. The puzzles can be solved by geometry puzzle lovers of all ages. The puzzler does not need to be an ace in geometry to solve them.
A warning: these puzzles can lead to a serious puzzle addiction! Enjoy the challenge!

(7/9)
The information given to solve the puzzle should be as minimal as possible, sometimes to the point that the reader might think that it is not possible to solve it. This is part of the challenge of puzzles.

(6/9)
Puzzles should not only be fun in their design, but they should also be fun to solve. Their shape should be appealing to arouse curiosity in the reader.

(5/9)
The first chapter, Solving a Puzzle, offers a typical puzzle, which then is solved step-by-step. It presents how geometry is used to solve it, and the logical thinking leading to the solution.

(4/9)
There are three types of geometry puzzles in this book:
• No shape-based puzzles, i.e., triangles, circles, etc.
• General shape-based puzzles, i.e., a hamburger, a bird, etc.
• Japanese shape-based puzzles, i.e., a samurai, a bonsai, etc.

(3/9)
Even if mathematical puzzles are new to the reader, this book is a great place to start. Puzzle solving is not only fun; it will also enhance the reader's understanding of mathematics. More experienced puzzlers will also find very challenging opportunities.

(2/9)
Mastering Geometry Puzzles has 5 chapters of puzzles, each one corresponding to a level of difficulty, from the very easy to the very hard.

Cover of the book Mastering Geometry Puzzles.

Back cover of the book Mastering Geometry Puzzles.

(1/9)
My new book 𝐌𝐚𝐬𝐭𝐞𝐫𝐢𝐧𝐠 𝐆𝐞𝐨𝐦𝐞𝐭𝐫𝐲 𝐏𝐮𝐳𝐳𝐥𝐞𝐬 will be released on April 9, 2026.
This book will challenge mathematical skills in a totally different way from the usual geometric puzzles. These 120 puzzles are visually intriguing.
#math #geometry #puzzle #book #MasteringGeometryPuzzles #BookSky