The values of a number of quantities are used in a mathematical formula. The quantity that should be most precise and accurate in measurement is the one

Write a note on combination of error.

Measure of two quantities along with the precision of respective measuring instrument  $A = 2.5\,m{s^{ - 1}} \pm 0.5\,m{s^{ - 1}}$, $B = 0.10\,s \pm 0.01\,s$ The value of $AB$ will be

In an experiment, the values of refractive indices of glass were found to be $1.54, 1.53,$$1.44,1.54,1.56$ and $1.45$ in successive measurements, then Mean absolute error is 

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

In a simple pendulum experiment for determination of acceleration due to gravity $(g)$, time taken for $20$ oscillations is measured by using a watch of $1\, second$ least count. The mean value of time taken comes out to be $30\,s$. The length of pendulum is measured by using a meter scale of least count $1\, mm$ and the value obtained is $55.0\, cm$. The percentage error in the determination of $g$ is close to  ........... $\%$