trapezoid QRST is dilated by a scale factor of 3.4 to create trapezoid Q'R'S'T'. The perimeter of trapezoid QRST is y units. What is the perimeter in units of trapezoid Q'R'S'T'?
The scale factor is 3.4, so all corresponding sides in the dilated trapezoid are 3.4 times the length of the corresponding sides in the original trapezoid.
Therefore, the perimeter of the dilated trapezoid is also 3.4 times the perimeter of the original trapezoid.
Since the perimeter of the original trapezoid is y units, the perimeter of the dilated trapezoid is 3.4y units.
Therefore, the perimeter of trapezoid Q'R'S'T' is 3.4y units. Answer: \boxed{3.4y}.