If you drop a pebble from 100metres how fast will it be going just before it hits the ground?

i've used the equation, time is equal to the square root of 2 times the distance divided by the acceleration of gravity, so, 2 times 100m = 200m, diveded by 9.81m/s2 = 20.39, and the square root of this is 4.51seconds. Now i have the time I just multiplied this by 9.81m/s2 and get the answer 44.24m/s. Is this right? it sounds about right but I have no way of checking. any help or pointers would be much appreciated.