
In figure (a), the springs are connected in series. Therefore,
Keq=K1+K2K1K2=K+2KK×2K=32K
Therefore, the time period
Ta=2πKeqm=2π32Km=2π2K3m
In figure (b), the springs are connected in parallel. Therefore,
Keq=K1+K2=3K
Therefore, the time period
Tb=2πKeqm=2π3Km
Now,
TbTa=29⇒Tb=32Ta=2s
Hence, x=2