AP EAMCET Engineering 2018 Apr 24 Shift 1 Paper

Let initially, both the oscillating particles are at mean position i.e., ,(x=0 at t=0)
The first particle is in same phase at given time instances. So, t=0s,3s,6s,9 s,12s, 15s,.....etc
The time period of second particle will be selected from the given options which give same phase of the both particles at t=15s,30s,45s,..... etc.
From option (1),
t=0s,1s,2s,3s,4s,5s,..... etc.
From option (2)
t=0s,1.5s,3s,4.5s,6s.... etc.
From option ( 3 ),
t=0s,2s,4s,6s,......etc
From option (4),
t=0s,2.5s,5s,7.5s,10s,12.5s,15s,...... etc.
So, the both particles are in same phase again at t=15s,30s,45s,...... etc only. Thus the time period must be 2.5s