Aria measured a line to be 20.9 inches long. If the actual length of the line is 19.2 inches, then what was the percent error of the measurement, to the nearest tenth of a percent?
The percent error is the absolute value of the difference between the actual length and the measured length, divided by the actual length, multiplied by 100.
The difference between the actual length and the measured length is 20.9 - 19.2 = 1.7 inches.
The percent error is (1.7 / 19.2) * 100 = 8.854166666666666 * 100 = 885.4.
Rounding to the nearest tenth, the percent error is 885.4 rounded to the nearest tenth of a percent = <<885.4=885.4>>885.4 to the nearest tenth of a percent is 885.4%. Answer: \boxed{885.4}.