Zero error of an instrument introduces

The radius of a sphere is measured to be $(7.50 \pm 0.85) \, cm$. Suppose the percentage error in its volume is $x$. The value of $x$,to the nearest integer is .....$\%$

If the error in measuring the diameter of a circle is $4\%$,the error in the radius of the circle would be (in $\%$)

The percentage error in the measurement of $g$ is $.....\%$ (Given that $g = \frac{4 \pi^2 L}{T^2}$,$L = (10 \pm 0.1) \, cm$,$T = (100 \pm 1) \, s$)

In an experiment,the values of refractive indices of glass were found to be $1.54, 1.53, 1.44, 1.54, 1.56$ and $1.45$ in successive measurements. The mean absolute error is:

Consider a series of measurements of the length of a box in an experiment. The readings are $2.4 \ m, 2.5 \ m, 2.6 \ m, 2.8 \ m, 3.0 \ m$. What would be the relative error?