A :-) for this question , we should apply
a = v - u by t
t = v - u by a
Given - u = 0
v = 100 m/s
a = 12 m/s^2
Solution -
t = v - u by a
t = 100 - 0 by 12
t = 100 by 12
( cut 12 and 100 because 2 x 50 = 100 ,
2 x 6 = 12 )
( cut 6 and 50 because 2 x 3 = 6 ,
2 x 25 = 50 )
t = 3 by 25
t = 0.12 sec
.:. The time is 0.12 sec.