"There is insufficient space on the device"--This is not duplicate My mobile is Micromax Canvas HD Plus .It has 4 GB inbuilt memory and 16 GB external memory card.I have selected SD Card as default location to install apps but still when I try to install app from Play Store it shows above error.My SD Card is nearly empty.

I searched a lot .Uninstalling Play store updates,Clearing Cache nothing worked.
It's not about how internal memory you have, it's about how big your /data partition is. Apps can only install to this partition, and even if you had your internal memory empty, apps wouldn't be able to fill this memory because they are only stored in /data. To fix this, you can try to resize partitions, but it's not simple, so be sure to know what you're doing before you corrupt your partitions.