Answer:
The error in the measurement was 17.9 %
Explanation:
In order to calculate the percentage error we need to find the absolute value of the error, wich is the difference between what Juan measured and the real length of the line. So we have error = 13.8 - 11.7 = 2.1 inches. In order to find the percentage we need to divide this value by the real length of the line and multiply it by 100. So we have:
error(%) = (2.1/11.7)*100 = 17.9 %