$$\sqrt\frac{?}{3136}=\frac{1}{2}$$​ Find the value of ?

Correct option is D

Given:
​$$\sqrt{\dfrac{?}{3136}} = \dfrac{1}{2} \\$$​
Formula Used:
​$$\text{If } \sqrt{\dfrac{x}{y}} = \dfrac{m}{n}, \text{ then } \dfrac{x}{y} = \dfrac{m^2}{n^2}$$​​
Solution:
​$$\sqrt{\dfrac{?}{3136}} = \dfrac{1}{2} \\\text{Squaring both sides} \\\dfrac{?}{3136} = \dfrac{1}{4} \\? = \dfrac{3136}{4} \\? = 784$$​​
The value of ? = 784