Chapter 16 - Electric Potential, Energy, and Capacitance - Learning Path Questions and Exercises - Exercises - Page 594: 44

3

The expression is $C=\kappa C_{0}$ where $C$ is the capacitance after the dielectric material is added, $C_{0}$ is the capacitance when the air is in between the plates and $\kappa$ is the dielectric constant of the material. $\implies \kappa=\frac{C}{C_{0}}=\frac{150\,pF}{50\,pF}=3$