The density of a material in the shape of a cube is determined by measuring three sides of the cube and its mass. If the relative errors in measuring the mass and length are respectively $1.5\%$ and $1\%$,the maximum error in determining the density is ........ $\%$

$A$ student uses a simple pendulum of exactly $1 \ m$ length to determine $g$,the acceleration due to gravity. He uses a stopwatch with a least count of $1 \ s$ for this and records $40 \ s$ for $20$ oscillations. For this observation,which of the following statement$(s)$ is (are) true?
$(A)$ Error $\Delta T$ in measuring $T$,the time period,is $0.05 \ s$
$(B)$ Error $\Delta T$ in measuring $T$,the time period,is $1 \ s$
$(C)$ Percentage error in the determination of $g$ is $5 \%$
$(D)$ Percentage error in the determination of $g$ is $2.5 \%$

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

The current-voltage relation of a diode is given by $I = (e^{1000V/T} - 1) \text{ mA}$,where the applied voltage $V$ is in volts and the temperature $T$ is in Kelvin. If a student makes an error of $\pm 0.01 \text{ V}$ while measuring the voltage to obtain a current of $5 \text{ mA}$ at $300 \text{ K}$,what will be the error in the value of current in $\text{mA}$?

$A$ physical parameter $a$ can be determined by measuring the parameters $b, c, d$ and $e$ using the relation $a = \frac{b^\alpha c^\beta}{d^\gamma e^\delta}$. If the maximum percentage errors in the measurement of $b, c, d$ and $e$ are $b_1\%, c_1\%, d_1\%$ and $e_1\%$ respectively,then the maximum percentage error in the value of $a$ determined by the experiment is:

Explain the error of a sum or a difference.