Each circle in this diagram is to be colored red, yellow, or blue.
No two circles joined by a line may be given the same color.
How many different colorings are possible?
Solution to the Problem:
The answer is 12 colorings.If you make the central circle red, the two circles on the left can only be blue and yellow, or yellow and blue, and similarly for the right-hand circles.
So, there are four ways to color this diagram if red is the center.
Similarly, there are four ways to color the diagram when the central circle is either yellow or blue, leading to 12 colorings in all.
Correctly solved by:
| 1. James Alarie | Flint, Michigan |
| 2. Sem Karaman | San Francisco, California |
| 3. Michael Reilly | Silver Spring, Maryland |