The number of perfect square numbers between 50 and 1000 is = ?

Answer: Option D

The first perfect square number after 50 is 64 $$\left(64=8^2\right)$$   and the last perfect square number before 1000 is 961 $$\left[961={\left(31\right)}^2\right]$$
So, the perfect squares between 50 and 1000 are the squares of numbers from 8 to 31.
(31 - 8) + 1 = 24
Clearly, these are 24 in number.