Answer:
11.42 %
Step-by-step explanation:
The formula for calculating percentage error
percentage error = observed value - actual value x 100
actual value
Percentage error = 3.9- 3.5 x 100
3.5
Percentage error = 0.4 x 100
3.5
Percentage error =0.1142 x 100
Percentage error = 11.42 %