Inverse of ratio

Question

Say I have two equations:

$$a = {b \over c} \\ d = {c \over b}$$

Now assume that I know the value of $b \over c$ (e.g. $4$), how would I then determine the value of $c \over b$?

Note: I do not require the values of $b$ and $c$, just their ratio value.

Answer 1

Just divide 1 by $\frac bc$:

$$d = \frac cb = \frac 1{\frac bc}=\frac 1a$$

Answer 2

HINT:

$$\frac cb = \frac 1{\frac bc}$$