Answer
$0.001~cm$, $0.0005~cm$, $0.00023$, $0.02\%$
Work Step by Step
For the measurement $2.135~cm$, we have:
The last digit $5$ is in the $0.001$ place, so the precision is $0.001~cm$.
The greatest possible error is one-half the precision:
$0.5\cdot 0.001 \ rpm=0.0005 \ cm$
The relative error is
$relative~error=\dfrac{greatest~possible~error}{measurement}$
$\frac{0.0005\ cm}{2.135\ cm}=0.00023$
The percent of error is $0.02\%$.
