How to remove an old version of Qt and keeping the new one?

Question

I have Ubuntu 16.04 installed on my PC (it has Qt Designer...etc preinstalled).
Today I installed Qt5.5 using these instructions.

When I open Qt Creator it detects two versions of Qt (Qt5.5 and Qt4.8.7).

My question is pretty simple: is it safe to purge the old version of Qt without destroying the new version?

Solution

Yes and no.

Yes, it is safe to remove one Qt version without effecting the other.

No, it is not safe to remove the old Qt version here since both versions are part of your system and are most likely installed because something on your system actually needs both versions. You can probably remove the Qt 4 development package though. Just try using your package manager.

Once the version is removed from your system (usually removing the developer package is enough) Creator should remove them from its list.