The area $'A'$ of a blot of ink is growing such that after $t$ second its area is given by $A = (3t^2 + 7)\,cm^2$. Calculate the rate of increase of area at $t = 2\, sec$. .......... $cm^2/s$
$6$
$17$
$12$
$19$
If $log_{10} (xy) = 2$, then the value of $xy$ is
The side of a square is increasing at the rate of $0.2\,cm / s$. The rate of increase of perimeter w.r.t. time is $...........\,cm / s$
The sum of the series $1+\frac{1}{4}+\frac{1}{16}+\frac{1}{64}+\ldots \ldots . \infty$ is