Charged capacitor connected to an uncharged capacitor

[Bolter]

Homework Statement:

Find the pd across the combined capacitors

Relevant Equations:

Q = CV

Hi there, tried doing this question but not sure if what I did for part b is right?

Appreciate any help! Thanks

 

[Merlin3189]

Yes. Fine.

As it's so simple (the numbers), you might like to do an intuitive check and say something like,
The 4 μF is double the 2 μF, so its like you end up with 3 caps of 2 μF in parallel sharing the same charge.
So each cap has 1/3 of the total charge and so must be charged to 1/3 of the voltage that the single 2 μF needed.