Answer:
Explanation:
Number the sides of the decagon: 1, 2, 3, 4, 5, 6, 7, 8, 9, and 10, from top (currently red) clockwise.
- The side number one can be colored of five different colors (red, orange, blue, green, or yellow): 5
- The side number two can be colored with four different colors: 4
- The side number three can be colored with three different colors: 3
- The side number four can be colored with two different colors: 2
- The side number five can be colored with the only color left: 1
- Each of the sides six through ten can be colored with one color, the same as its opposite side: 1
Thus, by the multiplication or fundamental principle of counting, the number of different ways to color the decagon will be:
- 5 × 4 × 3 × 2 ×1 × 1 × 1 × 1 × 1 × 1 = 120.
Notice that numbering the sides starting from other than the top side is a rotation of the decagon, which would lead to identical coloring decagons, not adding a new way to the number of ways to color the sides of the figure.
