The largest four digit number which is a perfect cube, is:

Answer: Option C

Explanation:

\begin{aligned}
= \sqrt{\frac{25}{16}}
\end{aligned}

\begin{aligned}
= \frac{\sqrt{25}}{\sqrt{16}}
\end{aligned}

\begin{aligned}
= \frac{5}{4}
\end{aligned}

\begin{aligned}
= 1\frac{1}{4}
\end{aligned}

Answer: Option D

Explanation:

L.C.M. of 21, 36, 66 = 2772

Now, 2772 = 2 x 2 x 3 x 3 x 7 x 11

To make it a perfect square, it must be multiplied by 7 x 11.

So, required number = 2 x 2 x 3 x 3 x 7 x 7 x 11 x 11 = 213444

Answer: Option A

Explanation:

\begin{aligned}
3600 = 2^3 \times 5^2 \times 3^2 \times 2
\end{aligned}
To make it a perfect cube it must be divided by
\begin{aligned}
5^2 \times 3^2 \times 2 = 450
\end{aligned}

Answer: Option D

Answer: Option C

Explanation:

\begin{aligned}
= \sqrt{248+\sqrt{64}}
\end{aligned}

\begin{aligned}
= \sqrt{248+8}
\end{aligned}

\begin{aligned}
= \sqrt{256}
\end{aligned}

\begin{aligned}
= 16
\end{aligned}