Ignoring air resistance . . .
-- Gravity adds 9.8 m/s to the speed of a falling object every second.
-- After falling for 3 sec, it's falling (3 x 9.8) = 29.4 m/s faster
than it was when it was dropped.
-- It started out with zero speed when it rolled off the top of the building,
so its speed is 29.4 m/s after 3 seconds.
-- Its average speed all the way down is
(1/2) (0 + 29.4) = 14.7 m/s .
-- After traveling for 3 sec at an average speed of 14.7 m/s,
it has traveled
(3 sec) x (14.7 m/s) = 44.1 meters .