A helicopter is flying horizontally with a speed v at an altitude h...

The aeroplane imparts $v$ velocity to the food packet horizontally when dropping. Horizontal range of food packet $= v \times \sqrt{\dfrac{2h}{g}}$
Also, Horizontal distance, travelled by aeroplane $= v \times \sqrt{\dfrac{2h}{g}}$ thus, vertical distance between aeroplane and person $= h$
distance $= \sqrt{\dfrac{2{v}^{2}h}{g} + {h}^{2}}$