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Complex proportionality
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### Direct Proportion involving squares, cubes and roots.

While this may seem to be more difficult, the process is almost the same as the last section. If you follow the method precisely, you will have no difficulties.

Questions using more complex forms of proportionality require us to think carefully about what is going on before starting to calculate. The phrases to look out for are:

1. $A$ is directly proportional to the square of $B$, which translates as $A \propto B^2$.
2. $P$ is directly proportional to the inverse of the square root of $Q$, which translates to $P \propto \frac{1}{\sqrt{Q}}$
3. $g$ varies as the inverse of $r$ squared, which translates as $g \propto \frac{1}{r^2}$. This is an example of an inverse square law. This one particularly, is based on the formula for calculating gravity and/or weight anywhere in the universe.