When multiplying or dividing by powers of ten, you can simply move the decimal right or left, respectively, based on the exponent in the power of ten.
Multiplication:
To multiply a decimal by a power of ten, move the decimal point to the right the same number of places as the number of the exponent in the power of ten.
Ex. Let's say we have the number 3.45 and want to multiply it by 10^2.
The exponent of the power of ten is 2, therefore we move the decimal right 2 places because we are multiplying.
3.45 → 345.
Division:
To divide a number by a power of ten, we move the decimal point to the left the same amount of times as the exponent.
Ex. Let's say we want to divide the decimal number 0.078 by 10^2
The exponent is 2 in the power of 10, therefore we move the decimal place 2 places to the left because we are dividing.
0.078 → 0.00078