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 least count of a stopwatch is $0.2\, s$. The time for $20\, oscillations$ of a pendulum is measured to be $25\, s$. The percentage error in the measurement of time will be ........ $\%$

The two specific heat capacities of a gas are measured as $C_P = (12.28 \pm 0.2) \text{ units}$ and $C_V = (3.97 \pm 0.3) \text{ units}$. Find the value of the gas constant $(R)$.

Two resistors of resistances $R_1 = (100 \pm 3) \,\Omega$ and $R_2 = (200 \pm 4) \,\Omega$ are connected in series. The maximum absolute error and percentage error in the equivalent resistance of the series combination are:

In an experiment to determine the acceleration due to gravity $g$,the formula used for the time period of a periodic motion is $T=2 \pi \sqrt{\frac{7(R-r)}{5 g}}$. The values of $R$ and $r$ are measured to be $(60 \pm 1) \text{ mm}$ and $(10 \pm 1) \text{ mm}$,respectively. In five successive measurements,the time period is found to be $0.52 \text{ s}, 0.56 \text{ s}, 0.57 \text{ s}, 0.54 \text{ s}$ and $0.59 \text{ s}$. The least count of the watch used for the measurement of time period is $0.01 \text{ s}$. Which of the following statement$(s)$ is(are) true?
$(A)$ The error in the measurement of $r$ is $10 \%$
$(B)$ The error in the measurement of $T$ is $3.57 \%$
$(C)$ The error in the measurement of $T$ is $2 \%$
$(D)$ The error in the determined value of $g$ is $11 \%$

State the rule for the error in the result due to multiplication and division of two physical quantities.