A technician has a plano-convex lens of glass with refractive index 1.6…

Step 1. Curved face silvered. $\dfrac{1}{F} = \dfrac{2(n - 1)}{R} + \dfrac{2}{R} = \dfrac{2n}{R} = \dfrac{3.2}{20\ \text{cm}}$, so $F = 6.25\ \text{cm}$.

Step 2. Plane face silvered. $\dfrac{1}{F} = \dfrac{2(n - 1)}{R} = \dfrac{1.2}{20\ \text{cm}}$, so $F = 16.7\ \text{cm}$.

Step 3. The image with the curved face silvered. We want $v$, so $\dfrac{1}{v} = \dfrac{1}{6.25\ \text{cm}} - \dfrac{1}{10\ \text{cm}} = 0.0600\ \text{cm}^{-1}$ and $v = 16.7\ \text{cm}$, a real image in front.

Step 4. The image with the plane face silvered. $\dfrac{1}{v} = \dfrac{1}{16.7\ \text{cm}} - \dfrac{1}{10\ \text{cm}} = -0.0400\ \text{cm}^{-1}$, so $v = -25.0\ \text{cm}$. The image is virtual, behind the mirror. The magnification is $m = -\dfrac{v}{u} = \dfrac{25.0\ \text{cm}}{10\ \text{cm}} = 2.50$, upright.