Question

Find a square of a natural number between 75 and 90.

Answer 1

We know that $8^2=64$ and ${10}^2=100$

Since $64$ and $100$ does not lie in the given range therefore square of $9$ may lie in this range.

We know that the square of a number ending with $9$ or $1$ ends with $1$ at its unit's place. Only $81$ is such a number that exists between the given range and which is also the square of number $9$.

Therefore, square between $75$ and $90$ is $81$.