Jules R. answered 11d
Former Engineer Turned Artist Turned Teacher
This gets tricky if you don't have the time given, but you do have the final velocity and you have the gravitational constant of g = 9.8 m/s2 and from these you can get what you need.
Freefall equation:
H = 1/2 gt2
But you don't have t. Here's how to derive it: if vfinal = gt, then t = vfinal / g
So substitute for t and plug and chug.
H = 1/2 g (vfinal/g)2 = 1/2 (9.8) (30/9.8)2 = 15 m tall building
Hope that helps.

Arturo O.
The final equation for H gives 45.92 m.11d