If $x = 10.0 \pm 0.1$ and $y = 10.0 \pm 0.1$,then $2x - 2y$ is equal to

The period of an oscillating simple pendulum is $T = 2 \pi \sqrt{\frac{\ell}{g}}$,where the length $\ell = 100 \text{ cm}$ with an error of $1 \text{ mm}$. The period $T = 2 \text{ s}$. The time for $100$ oscillations is measured by a stopwatch with a least count of $0.1 \text{ s}$. The percentage error in the gravitational acceleration $g$ is: (in $\%$)

During Searle's experiment,the zero of the Vernier scale lies between $3.20 \times 10^{-2} \text{ m}$ and $3.25 \times 10^{-2} \text{ m}$ of the main scale. The $20^{\text{th}}$ division of the Vernier scale exactly coincides with one of the main scale divisions. When an additional load of $2 \text{ kg}$ is applied to the wire,the zero of the Vernier scale still lies between $3.20 \times 10^{-2} \text{ m}$ and $3.25 \times 10^{-2} \text{ m}$ of the main scale,but now the $45^{\text{th}}$ division of the Vernier scale coincides with one of the main scale divisions. The length of the thin metallic wire is $2 \text{ m}$ and its cross-sectional area is $8 \times 10^{-7} \text{ m}^2$. The least count of the Vernier scale is $1.0 \times 10^{-5} \text{ m}$. The maximum percentage error in the Young's modulus of the wire is:

$A$ physical quantity $A$ is related to four observables $a, b, c,$ and $d$ as follows: $A = \frac{a^2 b^3}{c \sqrt{d}}$. The percentage errors of measurement in $a, b, c,$ and $d$ are $1\%, 3\%, 2\%,$ and $2\%$ respectively. What is the percentage error in the quantity $A$?

The acceleration due to gravity is measured on the surface of the Earth by using a simple pendulum. If $\alpha$ and $\beta$ are relative errors in the measurement of length and time period respectively,then the percentage error in the measurement of acceleration due to gravity is:

Zero error belongs to the category of