A toy of mass 0.50 kg hangs from a spring and stretches it by 8.0 cm…

A hanging spring rests at a stretch $d$ with $kd = mg$, and $T = 2\pi\sqrt{m/k} = 2\pi\sqrt{d/g}$. In parallel $k = k_1 + k_2$; in series $\dfrac{1}{k} = \dfrac{1}{k_1} + \dfrac{1}{k_2}$. A piece of a spring has a larger $k$: $k \times$ length stays the same.