This document discusses multiplying and dividing by powers of ten. It provides examples of multiplying and dividing whole numbers and decimals by powers of ten. The key rules are:
1) For multiplication, move the decimal point to the right when multiplying by a whole number power of ten, and to the left when multiplying by a decimal power of ten.
2) For division, move the decimal point to the left when dividing by a whole number power of ten, and to the right when dividing by a decimal power of ten.
3) Examples are provided to demonstrate applying these rules to calculate answers through mental math.