Connect all nine dots, without lifting pencil from the paper, using 4 straight lines
History of the Puzzle
The nine dot problem is a classic lateral thinking exercise that gained widespread popularity in the 1970's and 80's. Participants are presented with a set of dots arranged in a 3x3 grid and challenged to connect all nine dots, without lifting their pencil from the paper, using the fewest possible number of straight lines.
Copy the simple diagram above onto a piece of paper and give the puzzle a try.
The solution requires one to "think outside the box" and, some contend, that the nine dot problem served as the inspiration for this popular phrase.