diff --git a/piclib/prelude.scm b/piclib/prelude.scm
index 9c2b568f..6245f678 100644
--- a/piclib/prelude.scm
+++ b/piclib/prelude.scm
@@ -591,14 +591,6 @@
 
 ;;; 6.2. Numbers
 
-(define (floor/ n m)
-  (values (floor-quotient n m)
-	  (floor-remainder n m)))
-
-(define (truncate/ n m)
-  (values (truncate-quotient n m)
-	  (truncate-remainder n m)))
-
 ; (import (only (scheme inexact) sqrt))
 (import (scheme inexact))
 
diff --git a/src/number.c b/src/number.c
index be3eabce..b7b32aea 100644
--- a/src/number.c
+++ b/src/number.c
@@ -8,6 +8,7 @@
 
 #include "picrin.h"
 #include "picrin/string.h"
+#include "picrin/cont.h"
 
 static int
 gcd(int a, int b)
@@ -381,6 +382,26 @@ pic_number_floor_remainder(pic_state *pic)
   }
 }
 
+static pic_value
+pic_number_floor2(pic_state *pic)
+{
+  int i, j;
+  bool e1, e2;
+  double q, r;
+
+  pic_get_args(pic, "II", &i, &e1, &j, &e2);
+
+  q = floor((double)i/j);
+  r = i - j * q;
+
+  if (e1 && e2) {
+    return pic_values2(pic, pic_int_value(q), pic_int_value(r));
+  }
+  else {
+    return pic_values2(pic, pic_float_value(q), pic_float_value(r));
+  }
+}
+
 static pic_value
 pic_number_trunc_quotient(pic_state *pic)
 {
@@ -414,6 +435,26 @@ pic_number_trunc_remainder(pic_state *pic)
   }
 }
 
+static pic_value
+pic_number_trunc2(pic_state *pic)
+{
+  int i, j;
+  bool e1, e2;
+  double q, r;
+
+  pic_get_args(pic, "II", &i, &e1, &j, &e2);
+
+  q = trunc((double)i/j);
+  r = i - j * q;
+
+  if (e1 && e2) {
+    return pic_values2(pic, pic_int_value(q), pic_int_value(r));
+  }
+  else {
+    return pic_values2(pic, pic_float_value(q), pic_float_value(r));
+  }
+}
+
 static pic_value
 pic_number_gcd(pic_state *pic)
 {
@@ -780,8 +821,10 @@ pic_init_number(pic_state *pic)
   pic_defun(pic, "abs", pic_number_abs);
   pic_defun(pic, "floor-quotient", pic_number_floor_quotient);
   pic_defun(pic, "floor-remainder", pic_number_floor_remainder);
+  pic_defun(pic, "floor/", pic_number_floor2);
   pic_defun(pic, "truncate-quotient", pic_number_trunc_quotient);
   pic_defun(pic, "truncate-remainder", pic_number_trunc_remainder);
+  pic_defun(pic, "truncate/", pic_number_trunc2);
   pic_defun(pic, "modulo", pic_number_floor_remainder);
   pic_defun(pic, "quotient", pic_number_trunc_quotient);
   pic_defun(pic, "remainder", pic_number_trunc_remainder);