If the radius of a circle increases from $3 \, cm$ to $3.2 \, cm$,then the increase in the area of the circle is

The time period $T$ of a simple pendulum of length $l$ is given by $T=2 \pi \sqrt{\frac{l}{g}}$. If the length is increased by $2 \%$,then the approximate change in the time period is:

Consider the following statements:
$A$ is the relative error in the area of a square when the relative error in its side is $0.4$.
$B$ is the relative error in the volume of a sphere when the relative error in its radius is $0.3$.
$C$ is the relative error in the surface area of a closed cylinder whose height is equal to its radius,when the relative error in its height is $0.2$.
$D$ is the approximate error in $y = x^2 + x - 3$ when $x = 2$ and $\delta x = 0.1$.
The ascending order of the values of errors in these statements is:

The side of an equilateral triangle is $5$ units. In measuring the side,an error of $0.05$ units is made. Then the percentage error in measuring the area of the triangle is

There is an error of $\pm 0.04 \text{ cm}$ in the measurement of the diameter of a sphere. When the radius is $10 \text{ cm}$,the percentage error in the volume of the sphere is

If the radius of a spherical balloon increases by $0.1 \%$,then its volume increases approximately by (in $\%$)