A 1kg block attached to a spring vibrates with a frequency of 1Hz...

The frequency of $1kg$ block is $f = \dfrac{1}{2\pi}\sqrt{\dfrac{k}{m}} = 1 Hz$

$4{\pi}^{2} = \dfrac{k}{m},m = 1$

Spring constant, $k = 4{\pi}^{2}$

In parallel connection of springs, the equivalent spring constant is ${k}_{eq} = 2k$.



$f = \dfrac{1}{2\pi}\sqrt{\dfrac{K \times 2}{8}}$

Frequency of $8kg$ block is$= \dfrac{1}{2}Hz$