Arithmetic/Bases/Another Look at Decimal (Base 10)
In order to understand bases, you should look at decimal to see how they work first.
For example, look at the number 123:
The 1 in the 100s place means 1 x 100
1 x 100 = 100
The 2 in the 10s place means 2 x 10
2 x 10 = 20
100 + 20 = 120
The 3 in the 1s place means 3 x 1
3 x 1 = 3
100 + 20 + 3 = 123
Notice how 100 = 102, 10 = 101, and 1 = 100.