Hi Kapil,
8GB ram will speed up your system and good when you run multiple screen tcode at same time.
Below is good config change RAM.
Dell Inspiron 15-3542 Notebook
Operating System:Windows® 8.1
Processor:Intel Core i3-4030U
Memory:4GB -----------------> 8 GB
Display:15.6” Screen
Storage Drive:1TB Hard Drive
Optical Drive:DVDRW
Regards
Suraj