Question 5854
Yes, it is rational. Rational numbers are positive and negative numbers that can be expressed as a fraction.

-0.685 is {{{-685/1000}}}, a fraction, so it is rational. 

Any decimal numbr with limited number of digits is rational. Even some decimal numbers with infinite amount of digits are rational, if the digits form repeating pattern. For example, 

{{{0.333333333333 = 1/3}}}