Hello darkvelvet Originally Posted by

**darkvelvet** I get all the workings except for this:

A = kP^2.

What is k?

It is the 'constant of proportionality'. If $\displaystyle \displaystyle A$ is proportional to $\displaystyle P^2$, then we can write

$\displaystyle A = kP^2$, where $\displaystyle \displaystyle k$ is a constant.

Using your original method, you (correctly) got

$\displaystyle A = \dfrac{3P^2}{64}$

So $\displaystyle k = \frac{3}{64}$

As you'll see from my working, $\displaystyle \displaystyle k$ is eliminated in the subsequent equations, so you didn't really need to evaluate it.

Grandad