We have been given that
[tex]I = $54, P = $900, t = 18 \text{ months
}[/tex]
We know the formula,
[tex]I=Prt[/tex]
On substituting the given values, we get
[tex]54=900\cdot r\cdot \frac{18}{12}\\\\r=\frac{54\cdot 12}{900\cdot 18}\\\\r=\frac{1}{25}\\\\r=0.04\\\\r=4\%[/tex]
The annual rate interest is 4%
