Q24. Three capacitors of capacitances $25 \mu \mathrm {~F} , 30 \mu \mathrm {~F}$ and $45 \mu \mathrm {~F}$ are connected in parallel to a supply of 100 V . Energy stored in the above combination is E. When these capacitors are connected in series to the same supply, the stored energy is $\frac { 9 } { x } \mathrm { E }$. The value of $x$ is $\_\_\_\_$ .