Answer
We should increase $V$ by $~~4.9\%$
Work Step by Step
We can write an expression for the original amount of energy stored in the capacitor:
$E = \frac{1}{2}CV^2$
We can find the required potential difference $V_f$ if the stored energy is $1.1~E$:
$E_f = 1.1~E$
$\frac{1}{2}CV_f^2 = (1.1)~(\frac{1}{2}CV^2)$
$V_f^2 = 1.1~V^2$
$V_f = \sqrt{1.1}~V$
$V_f = 1.049~V$
We should increase $V$ by $~~4.9\%$.
