Download 9 digits / Android


The problem posed by ninedigits solutions consists in the organization of the numbers 1 to 9 in a square of 3 * 3 to make the sum of the numbers of the first two rows is equal to the bottom row.


This program is aimed at reflecting on the addition. The goal is to find results that meet the primary condition. We must be aware that after obtaining a correct result can be achieved more easily results having in mind the properties of the sum.


Ninedigits has 336 solutions. If the program could become be easy for some, then the goal would be to find valid solutions in which a lady could travel chess box containing 1 to 9 doing right moves in this chess game piece. According to our analysis, there are three solutions of this type. You can also find the solution, following the same conditions, but with the tower of chess: This combination of conditions is only one solution. The program displays graphically the fact that having these special results.


For to switch the numbers between them, you can click on two squares, and they become exchanged. You can also drag a number of other to swap them.


To the right of the main square, the program displays the operation. It is important to understand what the numbers represent the big picture. This is explained in the representation on the right. In this game, the box is interpreted as a sum. Above the representation of operation there are are small ones in gray. No solutions without carrying numbers. If you leave the mouse over the line sum, it appears the result of the sum of the squares of the first two rows.

In each column, if the sum of the first two boxes is equal to the lower box, the numbers appear cyan background. When a solution is found, all numbers, including the main square, the background appears cyan.


To the right of all there's a select box that displays the results. Clicking on each one of them, the program displays the obtained solution.


The ninedigits can save the results into the computer. It uses cookies. You can also retrieve the results obtained previously.

For this, the program asks for a name to save and retrieve the results. The results are stored in the computer itself.

The results will be saved over a year since the last result found. Unless security reasons, cookies are deleted from the computer. Then the results will disappear.


The ninedigits is based on an idea described in the book: "New Mathematical Diversions" by Martin Gardner published in 1966.



Ninedigits is compatible with all browsers. Has been programmed and tested mostly under Firefox, and this is probably the best browser to use it.

There's a version for Android 2.2 and up at:


Ninedigits workshop: Android version: ninedigits workshop

© 2012 Mathcats: Wendy Petti, Boni Córdoba and Maurici Carbó