# If I varies inversely with R and I = 0.25 when R = 18, which equation should be used to show this relationship?

$I = \frac{9}{2 \cdot R}$

#### Explanation:

We can construct our equation like
$I = \frac{k}{R}$

given that I=0.25 when R=18,

$0.25 = \frac{k}{18}$

$k = 18 \cdot 0.25 = 4.5 = \frac{9}{2}$

final equation is:

$I = \frac{9}{2 \cdot R}$