$ sudo apt-get update
$ sudo apt-get install qalculate-gtk 

qalculate-gtk is installed in your system.

Make ensure the qalculate-gtk package were installed using the commands given below,

$ sudo dpkg-query -l | grep qalculate-gtk *

You will get with qalculate-gtk package name, version, architecture and description in a table

qalculate-gtk package basic information: