Update book.tex

AllenDowney · web-flow · commit 0382071babff · 2017-07-18T16:34:43.000-04:00
diff --git a/book/book.tex b/book/book.tex
@@ -3568,8 +3568,7 @@ \section{Floor division and modulus}
 \end{verbatim}
 
 But we don't normally write hours with decimal points.  Floor
-division returns the integer number of hours, dropping the
-fraction part:
+division returns the integer number of hours, rounding down:
 
 \begin{verbatim}
 >>> minutes = 105
