PART 1.

Consider the 3 x 3 square array of black dots and devise a strategy for connecting all 9 dots with 4 straight lines without removing your pencil (or pen) from the paper.

 

Two incorrect solutions to this problem are presented in Examples A and B below. A is incorrect because only 8 of the 9 dots have been connected by the 4 connected lines. B shows 4 lines connecting all the dots, but it is also incorrect because drawing the 3rd and 4th line required lifting the pencil from the page twice.

Example A
Example B

Yes, there really are solutions...try your hand solving the problem, and then
click here to view an answer.

 

Preface | Introduction to Problem Solving | Problem Sets | Acknowledgments