Most of the laptops today, weigh less as the hard disk drives have found their replacement with solid state devices. The LCDs have been replaced by LED displays which have also made laptops today feel light.
The other factor that increases the weight of a laptop is the type of battery. 8-cell batteries are heavier than 6-cell, which makes laptop feel heavy.
It doesn’t matter how much does the dell inspiron 15r weight, as this comes under light weight category.