Problem Description

 

Place the digits 1 through 9 in the circles at right so that the value in any circle will be the sum of the digits in the circles connected from below.

   
Background & Techniques

Here is the second little puzzle program adapted from my most recent puzzle book acquisition,  Giant Book of Mensa Mind Challenges , Stirling Publications, 2003.   

The operation of the program is simple:  Drag digits to the circles until the conditions are satisfied.  Clearly, since there are nine digits and only seven circles, some of the circles will contain two digits.  Drag and drop digits on the left or right side of the circle, depending whether you are setting the left or right digit. 

The solution is not included as part of the program but if you really get stuck, I have included it as a sample problem with our Brute Force problem solver which uses exhaustive search to find solutions for a given set of equations and values.     

From the programming point of view, the coding techniques are similar to those used in the Added Corners puzzle, the only real complication being the requirement to keep track of the possibility  two digits in a circle and evaluating them appropriately when forming sums.       

Running/Exploring the Program 

Suggestions for Further Explorations

I wonder,  how many other graphs could be created using the 9 digits with other arrangements of circles and meeting some mathematical condition?   

 

Created March 1, 2006 

Modified: November 07, 2008

 

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