The most accurate reading of the length of a $6.28 \,cm$ long fibre is ............... $cm$

Write rule for error produced in result due to addition and subtraction of error.

The density of a solid metal sphere is determined by measuring its mass and its diameter. The maximum error in the density of the sphere is $\left(\frac{x}{100}\right) \% .$ If the relative errors in measuring the mass and the diameter are $6.0 \%$ and $1.5 \%$ respectively, the value of $x$ is

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 ........... $\%$

The errors in the measurement which arise due to unpredictable fluctuations in temperature and voltage supply are :

Time intervals measured by a clock give the following readings : 

$1.25 \;s , 1.24\; s , 1.27\; s , 1.21 \;s$ and $1.28\; s$ 

What is the percentage relative error of the observations?