Time t taken for the first drop to reach ground is determined from the following equation
h = (1/2) g t2
where h = 9 m , is the vertical distance travelled by the first drop and g is acceleration due to gravity
Between 4 drops , there are three equal intervals Δt.
Δt = ( 1.355 ) /3 = 0.452 s
Distance d3 of third drop from top of building is given as
Distance d2 of second drop from top of building is given as