I am not entirely familiar with the equation ninja'ing involving the floor operators. Here is my problem. I need to solve for $x$. Everything is an integer, including $x$:

$$ a - 1 = \lfloor {\frac{x - b}{b - c} \rfloor} $$

The wiki has a nice page on the floor operator, but I am new at equations involving floor manipulations, so I am not really sure how to go about isolating $x$ at this point, thereby solving for it. Thanks.

EDIT: This is not a homework problem. I am writing software that needs to solve this for a seismological problem.


1 Answer 1


Hint: $a - 1 = \lfloor {\frac{x - b}{b - c} \rfloor}$ if and only if $a - 1\le \frac{x - b}{b - c}<a $. So you have to solve this system of inequalities.

  • $\begingroup$ Doesn't this mean there are possibly more than one solution to the problem? $\endgroup$
    – Spacey
    Jan 2, 2014 at 16:14
  • $\begingroup$ @Spacey Of course, this is possible, there are clearly exactly $|b-c|$ solutions. $\endgroup$
    – Phira
    Jan 2, 2014 at 17:03

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