How do I know which version of Qt I am using? When I open Qt Creator it shows \"Welcome to Qt Creator 2.3\". In the build setting, however, it shows Qt Version 4.7.1.
You are using Qt version 4.7.1, because that is the version of the qmake.
You can also from shell type qmake -v to get it.
The other version, namely 2.3, is the version of Qt Creator, not of Qt