Answer:Percent error= 90.9%
Step-by-step explanation:
Percent error or percentage error is defined as the percentage of the difference between a measured value usually from an experiment and an exact value in comparison to the exact number.
its formula is thus
Percent error = experimental value - exact or actual value /exact value x 100
=(18.9 - 9.9 /9.9 ) x 100= 9/9.9) x 100
0.909 x 100 = 90.90 = 90.9%