Wrench falling from helicopter takes 9.0 s to reach ground

[McKeavey]

During construction of the Canada pavilion in Vancouver, a wrench fell out of a hovering helicopter and took 9.0 s to reach the ground.
How far was the helicopter from the ground?

I'd assume you find Vavg.
And put it into d = v/t
But when I do that I end up with d = 4.9.
The answer says it's 4.0 x 10^2 m AKA 400m.

What did I do wrong?
And there's no additional information given from the Q.

 

[rock.freak667]

You know that y=ut+0.5at².

Assume the initial velocity is zero.

You are given time, what is the height y?

 

[McKeavey]

Oh..
What would be wrong with using d = v/t though?

 

[rock.freak667]

Oh..
What would be wrong with using d = v/t though?

How you plan to go about finding 'v'?