Why is the error in a measurement expressed with both positive and negative signs?

$A$ physical quantity $C$ is related to four other quantities $p, q, r$ and $s$ as follows:
$C = \frac{pq^2}{r^3 \sqrt{s}}$
The percentage errors in the measurement of $p, q, r$ and $s$ are $1\%, 2\%, 3\%$ and $2\%$ respectively.
The percentage error in the measurement of $C$ will be . . . . . . $\%$.

The pressure on a square plate is measured by measuring the force on the plate and the length of the sides of the plate. If the maximum percentage error in the measurement of force and length are respectively $4\%$ and $2\%$,the maximum percentage error in the measurement of pressure is ....... $\%$

An experiment is performed to obtain the value of acceleration due to gravity $g$ by using a simple pendulum of length $L$. In this experiment,the time for $100$ oscillations is measured by using a watch of $1$ second least count,and the value is $90.0$ seconds. The length $L$ is measured by using a meter scale of least count $1$ mm,and the value is $20.0$ cm. The error in the determination of $g$ would be ........... $\%$.

If there is a positive error of $50\%$ in the measurement of velocity of a body,then the error in the measurement of kinetic energy is .............. $\%$

The percentage error in the measurement of a physical quantity $m$ given by $m = \pi \tan \theta$ is minimum when $\theta = \dots \dots \dots \dots \dots ^\circ$ (Assume that the error in $\theta$ remains constant).