The least number to be subtracted from $16800$ to make it a perfect square is

The value of $\frac{9^{2} \times 18^{4}}{3^{16}}$ is

If $a^{2}+b^{2}+\frac{1}{a^{2}}+\frac{1}{b^{2}}=4,$ then the value of $a^{2}+b^{2}$ will be

The value of $\frac{2.75 \times 2.75 \times 2.75 - 2.25 \times 2.25 \times 2.25}{2.75 \times 2.75 + 2.75 \times 2.25 + 2.25 \times 2.25}$ is:

If $N = \frac{\sqrt{7} - \sqrt{3}}{\sqrt{7} + \sqrt{3}}$,then what is the value of $N + \frac{1}{N}$?

What will come in the place of the question mark $(?)$ in the following expression?
$25.05 \times 123.95 + 388.999 \times 15.001 = ?$