To find the length of one of the sides of rhombus QRST, we can use the property that the diagonals of a rhombus bisect each other at right angles.
Given that:
- \( QS = 30 \)
- \( RT = 16 \)
Since the diagonals bisect each other, we can find the lengths of segments \( QU \) and \( RU \):
\[ QU = \frac{QS}{2} = \frac{30}{2} = 15 \] \[ RU = \frac{RT}{2} = \frac{16}{2} = 8 \]
Now, we can use the Pythagorean theorem to find the length of one side of the rhombus (let's call it \( s \)).
In triangle \( QUR \):
\[ s^2 = QU^2 + RU^2 \]
Substituting the values:
\[ s^2 = 15^2 + 8^2 \] \[ s^2 = 225 + 64 \] \[ s^2 = 289 \] \[ s = \sqrt{289} = 17 \]
Thus, the length of one of the sides of the rhombus is \( \boxed{17} \).