HP 39g+ - Manual (Page 36)

1-26 Getting started
2. Select Number Format, press to display the
options, and highlight Fraction.
3. Press to select the Number Format option, then
move to the precision value field.
4. Enter the precision value that you want to use, and
press to set the precision. Press to return
to HOME.
See “Setting fraction precision” below for more
information.
Setting fraction
precision
The fraction precision setting determines the precision in
which the hp 39g+ converts a decimal value to a fraction.
The greater the precision value that is set, the closer the
fraction is to the decimal value.
By choosing a precision of 1 you are saying that the
fraction only has to match 0.234 to at least 1 decimal
place (3/13 is 0.23076...).
The fractions used are found using the technique of
continued fractions.
When converting recurring decimals this can be
important. For example, at precision 6 the decimal
0.6666 becomes 3333/5000 (6666/10000) whereas
at precision 3, 0.6666 becomes 2/3, which is probably
what you would want.
For example, when converting .234 to a fraction, the
precision value has the following effect: