Chapeter 3/7 physics?

Question

A supply plane needs to drop a package of food to scientists working on a glacier in Greenland. The plane flies 120 m above the glacier at a speed of 100 m/s

How far short of the target should it drop the package?

Answer 1

h = 1/2at^2

2h/a = t^2

(120m)/(9.8 m/s^2) = t^2

12.245 s^2 = t^2

t = 3.5 seconds

d = vt = (100m/s)(3.5s)

d = 350 meters