The plates of a parallel plate capacitor are separated by d. Two slabs of different dielectric constant K_1 and K_2 with thickness 3/8 d and d/2,…

The plates of a parallel plate capacitor are separated by $\displaystyle d$. Two slabs of different dielectric constant $\displaystyle K_1$ and $\displaystyle K_2$ with thickness $\displaystyle \frac{3}{8} d$ and $\displaystyle \frac{d}{2}$, respectively are inserted in the capacitor. Due to this, the capacitance becomes two times larger than when there is nothing between the plates. If $\displaystyle K_1=1.25 K_2$, the value of $\displaystyle K_1$ is :