## 25 Jun 2017

### Calypso

Algebraic surface of degree $3$ generated by the algebraic equation $x^2+y^2z=z^2$.

## 24 Jun 2017

### Traffic Lights

Game invented by Alan Parr in $1998$. The game consists of a board $3 \times 4$ and $24$ stones, $8$ of each color.

The goal of the game is to be the first to be able to align three pieces of the same color horizontally, vertically or diagonally.

Rules

Each player in turn can make one of the following moves: place a green stone on an empty board cell, replace a green stone that is already on the board with a yellow stone or replace a yellow stone that is already on the board by a red stone. The order of the colors is the same as the lights of a traffic light, and the red stones can not be replaced.

## 23 Jun 2017

### Challenge 21

Write $2017$ with the digits $1$ to $9$, except the $9$, using them all and separately, in increasing order, with the operations addition, subtraction, multiplication, division, power of $2$, power of $3$, square root, cubic root and factorial. Parenthesis are allowed.

Coming soon

## 22 Jun 2017

### Eiffel Tower

The Eiffel Tower is a wrought iron lattice tower on the Champ de Mars in Paris, France. It was completed in $15$ March $1889$ as the entrance to the $1889$World's Fair. It is named after the engineer Gustave Eiffel $(1832-1923)$, whose company designed and built the tower.

## 19 Jun 2017

### Tabachin Ribbon by Yvonne Domenge

Tabachin Ribbon ($2010)$ is a sculpture by Mexican artist Yvonne Domenge $(1946)$, located at Fort Worth, Texas, USA.

## 12 Jun 2017

### Calyx

Algebraic surface of degree $5$ generated by the algebraic equation $x^2+y^2z^3=z^4$.

## 11 Jun 2017

### Ten

$10$ é a base do sistema numeral decimal.

$10$ é um número triangular uma vez que $1+2+3+4=10$.

O decágono é um polígono com $10$ lados.

O decaedro é um poliedro com $10$ faces.