How to rotate multiple images at once in Lightroom?

To flip images taken upside down do this:

In Lightroom:

In grid view, select the group of photos using shift+right-click,

then press and hold Control/command and Photo / flip vertical.

Wallla.... perfect. 

I took images of  sisters laying on a bed with their new baby sister, but I didn't have enough room to  stand or use a ladder, so I just took them upside down. I am glad I found the answer before my reply. It helped me. Thanks.