The following observations were taken for determining surface tension $T$ of water by capillary method:

diameter of capillary, $D= 1.25 \times 10^{-2}\; m$

rise of water, $h=1.45 \times 10^{-2}\; m $ 

Using $g= 9.80 \;m/s^2$ and the simplified relation $T = \frac{{rhg}}{2}\times 10^3 N/m$ , the possible error in surface tension is ........... $\%$

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 $(60 \pm 1) \mathrm{mm}$ and $(10 \pm 1) \mathrm{mm}$, respectively. In five successive measurements, the time period is found to be $0.52 \mathrm{~s}, 0.56 \mathrm{~s}, 0.57 \mathrm{~s}, 0.54 \mathrm{~s}$ and $0.59 \mathrm{~s}$. The least count of the watch used for the measurement of time period is $0.01 \mathrm{~s}$. 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 $11 \%$

The percentage errors in quantities $P, Q, R$  and $S$  are $0.5\%,\,1\%,\,3\%$  and  $1 .5\%$ respectively in the  measurement of a physical quantity $A\, = \,\frac{{{P^3}{Q^2}}}{{\sqrt {R}\,S }}$ . the maximum percentage error in the value of $A$  will be ........... $\%$

If the percentage errors in measuring the length and the diameter of a wire are $0.1 \%$ each. The percentage error in measuring its resistance will be:

What is least count ? What is called least count error ?

The random error in the arithmetic mean of $100$ observations is $x$; then random error in the arithmetic mean of $400$ observations would be