Chosen Solution

can i put 1 2 ram and 1 4 ram in my 27" i5 imac?

According to Mactracker your computer can accept up to 16 GB of ram and I don’t see any requirement for matching. That being the case I would say yes you can use one each of 2 GB and 4 GB of ram.

My iMac is a “Core i5” 2.8 27-Inch (Mid-2010) Specs. Today with 8GB of RAM (2GB X 4). My question is similar: Can I use 2 GB x 2 + 4 GB x 2, totaling 12 GB? Thanks!