Two charged capacitors connected in series
The initial condition:
$$Q_1=C_1U_1= 10^{-6}$$
$$Q_2=C_2U_2= 10^{-5}$$
$$U_1=U_2=1$$

The final state:
$$Q=C_1\cdot U_1=C_2\cdot V_{final}$$
$$U_1+V_{final}=1$$

Solving the system: $$V_{final}=\frac{C_1}{C_1+C_2}$$