An eight-digit number divisible by $9$ is to be formed using digits from $0$ to $9$ without repeating the digits. The number of ways in which this can be done is: (in $(7!)$)

$\int_0^{\pi / 2} \frac{d x}{1+\tan ^3 x}$ is equal to :

From which plant is cocaine obtained?

$A$ radioactive sample of $U^{238}$ decays to $Pb$ through a process for which the half-life is $4.5 \times 10^9 \text{ years}$. What is the ratio of the number of nuclei of $Pb$ to $U^{238}$ after a time of $1.5 \times 10^9 \text{ years}$? (Given $2^{1/3} = 1.26$)

The number of atoms in $100 \text{ g}$ of an $fcc$ crystal with density $d = 10 \text{ g/cm}^3$ and cell edge equal to $100 \text{ pm}$ is equal to:

In the circuit given below,$V(t)$ is the sinusoidal voltage source. The voltage drop $V_{AB}(t)$ across the resistance $R$ is: