Error analysis the length of an object is exactly 20 cm. a student says that a measurement of 19 cm represents a percent error of 95%, while a measurement of 21 cm represents a percent error of 105%. explain what the student did wrong. what are the correct percent errors?

Percent errors are calculated by dividing the absolute value of the errors by the exact length. What the student did wrong here is that he or she divided the given measurements by the exact lengths, which should not be the case. 

Correct percent errors:
 19 cm
           percent error = (I19 - 20I / 20) x (100%)  = 5%
 21 cm
           percent error = (I21 - 20I / 20) x (100%) = 5%