Command line calculator that keeps fractional values

You can set the length of the fractional part with scale=n.

The command echo 'scale=20;752/447' | bc yields:

1.68232662192393736017

Note that even if the number fits within the scale, additional zero's might be appended:

scale=20
1/2
.50000000000000000000

Unfortunately, there is always a rounding issue:

scale=50
1/3*3
.99999999999999999999999999999999999999999999999999

calc (I believe from package apcalc) does the same as bc, but does not round. It displays similarly to bc, but unlike bc, it understands scientific notation. Example:

> calc
C-style arbitrary precision calculator (version 2.12.3.3)
Calc is open software. For license details type:  help copyright
[Type "exit" to exit, or "help" for help.]

; a=234
; b=a/7
; b
    ~33.42857142857142857143
; c=b/1e20
; c
    ~0.00000000000000000033
; c*1e10
    ~0.00000000334285714286
; 

Compare with bc:

> bc -l
bc 1.06.95
Copyright 1991-1994, 1997, 1998, 2000, 2004, 2006 Free Software Foundation, Inc.
This is free software with ABSOLUTELY NO WARRANTY.
For details type `warranty'. 
a=234
b=a/7
b
33.42857142857142857142
c=b/10^20
c
.00000000000000000033
c*1e10
(standard_in) 6: syntax error
c*10^10
.00000000330000000000

A little search turns up lots of results, not all of which are relevant, but I am sure that a few trials will get you exactly what you want (wcalc, for instance):

aptitude search calc
i   apcalc                               - Arbitrary precision calculator (original name: calc)
i A apcalc-common                        - Arbitrary precision calculator (common files)
p   apcalc-dev                           - Library for arbitrary precision arithmetic
p   bandwidthcalc                        - file transfer time calculator written in GTK+
p   calcoo                               - Scientific calculator (GTK+)
p   calcurse                             - text-based calendar and todo manager
p   concalc                              - console calculator
p   extcalc                              - multifunctional scientific graphic calculator
p   gcalcli                              - Google Calendar Command Line Interface
i   gcalctool                            - GNOME desktop calculator
p   ipcalc                               - parameter calculator for IPv4 addresses
p   ipv6calc                             - small utility for manipulating IPv6 addresses
p   kcalc                                - calculator for KDE 4
p   keurocalc                            - universal currency converter and calculator - binary package
p   keurocalc-data                       - universal currency converter and calculator - data package
p   lcalc                                - a program for calculating with L-functions
p   libcolor-calc-perl                   - Perl module for simple calculations with RGB colors
p   libdate-calc-perl                    - Perl library for accessing dates
p   libdate-pcalc-perl                   - Perl module for Gregorian calendar date calculations
p   libmath-basecalc-perl                - Convert numbers between various bases
p   libmath-calc-units-perl              - Human-readable unit-aware calculator
p   libmath-calculus-differentiate-perl  - Algebraic Differentiation Engine
p   libmath-calculus-expression-perl     - Algebraic Calculus Tools Expression Class
p   libmath-calculus-newtonraphson-perl  - Algebraic Newton Raphson Implementation
p   libticalcs-dev                       - Texas Instruments calculator communication library [development files]
p   libticalcs2-7                        - Texas Instruments calculator communication library
p   libwww-google-calculator-perl        - Perl interface for Google calculator
p   octave-physicalconstants             - provide physical constants values in Octave
i   openoffice.org-calc                  - office productivity suite -- spreadsheet
v   openoffice.org2-calc                 -
p   python-ipcalc                        - perform IP subnet calculations
v   python2.6-ipcalc                     -
p   r-cran-epicalc                       - GNU R Epidemiological calculator
p   rpncalc                              - RPN calculator trying to emulate an HP28S
p   science-numericalcomputation         - Debian Science Numerical Computation packages
p   sipcalc                              - Advanced console-based ip subnet calculator
p   subnetcalc                           - IPv4/IPv6 Subnet Calculator
p   sugar-calculate-activity             - calculate activity for the Sugar graphical shell
p   tapecalc                             - a full-screen tape editor that lets the user edit a calculation
p   transcalc                            - microwave and RF transmission line calculator
p   wcalc                                - A flexible command-line scientific calculator
p   wmcalclock                           - A dock.app which simply tells time and date
p   xsmc-calc                            - Smith Chart calculator for X

I would suggest using Python as a command-line calculator:

$ python
>>> from math import *
>>> help(sin)
    sin(x)

    Return the sine of x (measured in radians).

Also I would recommend IPython or IDLE. Both hugely improve usability of the standard shell.

Update: use python3 to avoid truncation surprises:

$ python2.7

>>> 10/3
3

$ python3

>>> 10/3
3.3333333333333335