"29. The total running cost of a ship per hour is £ (13 + $v^{2}$/52) where $v$ knots is the speed. if £ $C$ is the cost per nautical mile, write down an equation expressing $C$ in terms of $v$..."
So, we know the cost in £ h$^{-1}$. We need the cost in £ mi$^{-1}$. Additionally, the cost is expressed in terms of $v$ which is given in units of mi h$^{-1}$.
On the face of it, I thought (and I haven't got much experience of doing this), all I have to do is divide by $v$ mi h$^{-1}$:
$\dfrac{\text{£}\,x\ \text{h}^{-1}}{y \text{ mi h}^{-1}} = \text{£}\,z\text{ mi}^{-1}$
This gives the right answer:
$$\frac{13}{v} + \frac{v}{52}$$
But I don't know how to lay it out. I know the question says "write down" - but if only for own benefit, I'd still like to know how to do it nicely.
