Hello,
First hello to all, this is my first post in any forum, in last a few years. Just started to learn Blender, I installed in my xUbuntu lap top :). I want to make room from this cube, I remove top face. now I want to make room, on the left side, but I do not know how to create with dimensions, 4.5m with 5.60m. I can make room, with CTRL + R, but dimension is not precise.
Thank you in advance 
Have u set Units presets to meters in the Scene Settings?
Thank you for your replay, but you did not understand my question, yes I have configure units :). How can I make room with planed dimensions. Now I now how to make room but with approximately, but not precise dimensions. I have big cube and I want to subdivide with a few rooms different size. In my photo I do not see, any size of left or right part of cube. I hope so I better explain now 
Could make the floor plan first, then extrude the walls up. There’s object dimensions in 3d view properties but if you change them, apply the scale afterwards with ctrl+A -> scale to make the mesh match. In edit mode there’s edge length display there too.
Could also try archimesh addon.
“I installed in my xUbuntu lap top” Blender doesn’t need installing, which means you installed one from repo. Bad move, use the official from the website, especially when asking questions and/or troubleshooting. Don’t crop screenshots. Blender can save a screenshot, it’s in the window menu.
Not obsessing about absolute precision would also be wise. This is polygonal modeling which is approximation, and the precision required is for visual purposes. In other words, not a CAD.
Love that last sentience!
i agree, blender sucks at precision.
yes, blender is no CAD program. but in most cases it’s possible to be precise too if you want.
after ctrl-r you could simply set the x value in the n-panel with the new edges still selected. or you could first move the new edges fully to one side and then use edge slide. there are many ways to achieve the goal.
