Calculate the mean percentage error in five observations: $80.0, 80.5, 81.0, 81.5, 82.0$. (in $\%$)

An experiment measures quantities $a, b$ and $c$,and quantity $X$ is calculated from $X = ab^2 / c^3$. If the percentage errors in $a, b$ and $c$ are $\pm 1\%, \pm 3\%$ and $\pm 2\%$,respectively,then the percentage error in $X$ will be

What is the estimation of error? Write the methods for estimation.

The temperatures of two bodies measured by a thermometer are $t_{1} = 20^{\circ}C \pm 0.5^{\circ}C$ and $t_{2} = 50^{\circ}C \pm 0.5^{\circ}C$. Calculate the temperature difference and the error therein.

The outer and inner radii of a hollow cylinder are $(4.23 \pm 0.01) \text{ cm}$ and $(3.89 \pm 0.01) \text{ cm}$ respectively. What is the thickness of the wall of the cylinder?

The dimensions of a cone are measured using a scale with a least count of $2 \text{ mm}$. The diameter of the base and the height are both measured to be $20.0 \text{ cm}$. The maximum percentage error in the determination of the volume is. . . . .