The time the package travels horizontally is equal to the time it takes to hit the ground. This can be calculated using:
s = ut + 1/2 at²; u is 0
480 = 4.9t²
t = 9.90 seconds
Horizontal distance = horizontal speed x time
The speed will be converted to m/s from km/h
= 180 km/hr x 1000m/km x 1hr/3600 seconds x 9.90 seconds
= 495 m