It’s simple, but effective for command line addicts

If it’s not already installed, install it by using:

sudo apt install bc

then run bc and type any calculations you want. I wrote for example

$ bc
 bc 1.07.1
 Copyright 1991-1994, 1997, 1998, 2000, 2004, 2006, 2008, 2012-2017 Free Software Foundation, Inc.
 This is free software with ABSOLUTELY NO WARRANTY.
 For details type `warranty'. 
 3.65*549
 2003.85

That’s it, Enjoy!

Source: https://fedoramagazine.org/bc-command-line-calculator/