What is the sum of first $30$ odd natural numbers?

Find out the value of $\sqrt{350}$ to the nearest whole number.

Simplify: $\sqrt{15612+\sqrt{154+\sqrt{225}}}$.

Find the value of ${\left(39+21\right)}^2$.

Find the value of $\sqrt{0.0081}$

Find the length of the diagonal of a rectangle with dimensions $20 \mathrm{m}$ by $15 \mathrm{m}$.

Find the least number by which $216$ must be divided to make the result a perfect square.

How many square numbers lie between $81$ and $225$? Also, find them.

If the area of a square is $38.44 \mathrm{sq} \mathrm{cm}$, then find the side of the square.