The system of numbers that you use is called the decimal system and is based on powers of ten ( base ten system). Each place in the place value grid is ten times the value of the place to the right of it. Every number to the right of the decimal point is a decimal fraction (a fraction with a denominator of 10, 100, 1,000, and so on).
On the place value grid (see the following chart), notice that 
can be written as ten to a negative exponent, 10 –1. Similarly, 
can be written as ten to a negative exponent, 10 –2.
