The temperatures of two bodies measured by a thermometer are $t_1 = 20^{\circ}C \pm 0.5^{\circ}C$ and $t_2 = 50^{\circ}C \pm 0.5^{\circ}C$. The temperature difference and the error therein are:

If the length of a cylinder is $l = (4.00 \pm 0.01) \; cm$,radius $r = (0.250 \pm 0.001) \; cm$,and mass $m = 6.25 \pm 0.01 \; g$,calculate the percentage error in the determination of density.

Three students $S_{1}, S_{2}$ and $S_{3}$ perform an experiment for determining the acceleration due to gravity $(g)$ using a simple pendulum. They use different lengths of pendulum and record time for different number of oscillations. The observations are as shown in the table.

Student No.	Length of pendulum $(cm)$	No. of oscillations $(n)$	Total time for oscillations $(s)$	Time period $(s)$
$1.$	$64.0$	$8$	$128.0$	$16.0$
$2.$	$64.0$	$4$	$64.0$	$16.0$
$3.$	$20.0$	$4$	$36.0$	$9.0$

(Least count of length $= 0.1 \, cm$,least count for time $= 0.1 \, s$)
If $E_{1}, E_{2}$ and $E_{3}$ are the percentage errors in $g$ for students $1, 2$ and $3$ respectively,then the minimum percentage error is obtained by student no. ....... .

$A$ force $F$ is applied on a square plate of side $L$. If the percentage error in determining $F$ is $3 \%$ and that in $L$ is $2 \%$,then the percentage error in determining the pressure is (in $\%$)

$A$ physical quantity $S$ is related to four observables $a, b, c$, and $d$ as $S = \frac{\sqrt{a} b}{c^3 d^4}$. If the percentage errors of measurement in $a, b, c$, and $d$ are $2 \%$, $1 \%$, $1 \%$, and $1 \%$ respectively, then the percentage error in the quantity $S$ is: (in $\%$)

Two resistances are given as $R_1 = (10 \pm 0.5) \ \Omega$ and $R_2 = (15 \pm 0.5) \ \Omega$. The percentage error in the measurement of equivalent resistance when they are connected in parallel is (in $\%$)