Below are six circles. It is possible to move just one circle and end up with four straight rows of three circles each. Show how to do it.
Solution
The trick is to realize that you already have two rows of three; one is composed of circles one, four, and six; one is composed of circles three, four, and five. By connecting circles one and five, then connecting circles three and six, and then extending those two lines until they join, we find the spot to which we must move circle two. Here is the solution with lines drawn to show the four rows:
