To find a rational number with one decimal place that is between \(\sqrt{17}\) and \(\sqrt{18}\), we first need to approximate the square roots of these two numbers.
Calculating the square roots:
\[ \sqrt{17} \approx 4.123 \]
\[ \sqrt{18} \approx 4.243 \]
Now we need to find a rational number with one decimal place that lies between these two values. We can look for a decimal number in the range \(4.123\) to \(4.243\).
The possible candidates with one decimal place are \(4.1, 4.2\).
Both \(4.1\) and \(4.2\) are between \(4.123\) and \(4.243\).
Thus, a rational number with one decimal place that is between \(\sqrt{17}\) and \(\sqrt{18}\) is:
\[ \boxed{4.2} \]