It depends on which model 15R you have.  Some are 8G, some 16.  What's the full model number (i.e., Inspiron 5520, 5720, etc.)?

dell inspiron 15r 2106slv (5520)

and for inspiron 5720 ... which is the maximum supported memory ... can i use two modules of these? http://www.ec.kingston.com/ecom/configurator_new/partsinfo.asp?root=us&LinkBack=&ktcpartno=KTD-L3C/8G&id=1

Hi bar_budo,

Inspiron 5720/17R has 2 SODIMM memory slots which support:

• DDR3 DIMM at 1333 MHz with Sandy Bridge Processors
• DDR3 DIMM at 1600 MHz with Ivy Bridge Processors

Inspiron 5720/17R supports a maximum of 8 GB system memory with 4 GB memory in each slot. The memory you have shared is a single 8GB memory and might not work with the system.

For installing/replacing memory, you may refer to owner's manual Here.

Hope this helps. 

You're wrong. The 15R 5520 has a max of 16GB's RAM.

http://www.crucial.com/upgrade/Dell-memory/Inspiron+Laptops%2FNotebooks/Inspiron+15R+(5520)-upgrades.html

I want to upgrade to 16GB on my Inspiron 17r 5720... it seems unsupported by your answer? why?

Same situation for me. Apparently, 16 gigs are not supported. I though the limitation came from 32 bits. but now I have 64 bits windows 10.