Question

the ratio of distance moved by a free falling body from rest in 3 and 4 sec will be?

Answer 1

atmosphere is generalised at 9 metres per second per second (i.e. increasing another 9 metres per second EVERY second).  So your speed goes from 9m/s to 18m/s to 27m/s over 3 seconds.

Answer 2

5:7 is the ratio of distance between 3rd second and 4th second
(2n1 -1):(2n2 -1)
(2*3-1):(2*4-1)
5:7