Find the LCD 5/(10^3) ; 9/(10^6)

Raise ${\displaystyle 10}$ to the power of ${\displaystyle 3}$.

Cancel the common factor of ${\displaystyle 5}$ and ${\displaystyle 1000}$.

Raise ${\displaystyle 10}$ to the power of ${\displaystyle 6}$.

Find the values of the numerical part of each term. Select the largest one, which in this case is ${\displaystyle 1000000}$. Multiply them together to get the current total. In this case, the current total is ${\displaystyle 200000000}$.

Check each value in the numerical part of each term against the current total. Since the current total is evenly divisible, return it. That is the least common denominator of the numerical part of the fraction.