(2) How does base 10 compare with base 20?
The base 10 system that is used in the U.S. and most other countries today is based on powers of 10. The digits of 352 represent 3x100 + 5x10 + 2x1. 100 is 102, 10 is 101 and 1 is 100. Numbers in our base 10 system are written horizontally with the leftmost digit representing the highest power of 10. In the vigesimal system, the three place values would be for the number of 400’s (which is 202), the number of 20’s (which is 201) and the number of one’s (which is 200). In the Mayan vigesimal system, place values are written vertically with the one’s place at the bottom and the highest power of 20 at the top. It is interesting that this vigesimal system used by the Mayans originated with the Zapotecs of Oaxaca 1100 years before the Mayans did. The Hindu-Arabic number positional notation first occurred 1400 years after the Zabotecs’ positional vigesimal system.
In the "Vigesimal multiplication table" at right, the letters A through J are used to represent the single digit values of 10 through 19. Notice that the last number in the top row is "10." The 1 represents the fact that there is one 20, and the 0 represents that there are 0 ones.