Very often I need a simple command line calculator to do some simple math for my accounting or economics classes. Usually I don't need anything more complicated than the simple arbitrary precision calculator bc. The bc is very intuitive to use, after you learn to set the precision used in calculations:
This sets the precision to five digits. Unless you define the precision bc will default to integer results which would not provide especially precise results. After setting the precision, bc is very intuitive to use. For example:
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A lot more information can be found with man bc, as usual.