The period of oscillation of a simple pendulum in an experiment is recorded as $2.63\, s, 2.56\, s, 2.42\, s, 2.71\, s$,and $2.80\, s$ respectively. The average absolute error is ......... $s$.

$Assertion$ : The error in the measurement of radius of the sphere is $0.3\%$. The permissible error in its surface area is $0.6\%$.
$Reason$ : The permissible error is calculated by the formula $\frac{\Delta A}{A} = \frac{4\Delta r}{r}$.

Four persons measure the length of a rod as $20.00 \ cm$,$19.75 \ cm$,$17.01 \ cm$,and $18.25 \ cm$. The relative error in the measurement of the average length of the rod is:

The energy of a system as a function of time $t$ is given as $E(t)=A^2 \exp(-\alpha t)$,where $\alpha=0.2 \ s^{-1}$. The measurement of $A$ has an error of $1.25 \%$. If the error in the measurement of time is $1.50 \%$,the percentage error in the value of $E(t)$ at $t=5 \ s$ is

$A$ body travels uniformly a distance of $(13.8 \pm 0.2) \ m$ in a time $(4.0 \pm 0.3) \ s$. The percentage error in velocity is ......... $\%$

Quantity $Z$ varies with $x$ and $y$ according to the equation $Z = x^2y - xy^2$,where $x = 3.0 \pm 0.1$ and $y = 2.0 \pm 0.1$. The value of $Z$ is: