How to calculate the time of a falling object

The question briefly is;
An aircraft is dropping packages onto a island, and the aircraft is 150m at height, how long does it take the package to fall 150m?


If anyone can solve this and explain, would be appreciated.

Thanks

time of flight T = square root of ( 2 h/ g) = square root of ( 2x150 /9.8 ) = 5.53 sec.