Index: src/java/org/apache/poi/ss/formula/functions/MathX.java
===================================================================
--- src/java/org/apache/poi/ss/formula/functions/MathX.java	(revision 1611659)
+++ src/java/org/apache/poi/ss/formula/functions/MathX.java	(working copy)
@@ -19,6 +19,8 @@
 
 import org.apache.poi.ss.util.NumberToTextConverter;
 
+import java.math.BigDecimal;
+
 /**
  * @author Amol S. Deshmukh < amolweb at ya hoo dot com >
  * This class is an extension to the standard math library
@@ -108,10 +110,9 @@
 
         if (Double.isNaN(n) || Double.isInfinite(n)) {
             retval = Double.NaN;
+        } else {
+            retval = new BigDecimal(NumberToTextConverter.toText(n)).setScale(p, java.math.RoundingMode.DOWN).doubleValue();
         }
-        else {
-            retval = java.math.BigDecimal.valueOf(n).setScale(p, java.math.RoundingMode.DOWN).doubleValue();
-        }
 
         return retval;
     }
Index: src/testcases/org/apache/poi/ss/formula/functions/TestMathX.java
===================================================================
--- src/testcases/org/apache/poi/ss/formula/functions/TestMathX.java	(revision 1611659)
+++ src/testcases/org/apache/poi/ss/formula/functions/TestMathX.java	(working copy)
@@ -709,7 +709,13 @@
     public void testRoundDown() {
         double d = 0;
         int p = 0;
-        
+
+        d = 396d * 2.32d; p = 9;
+        assertEquals("roundDown ", 918.72d, MathX.roundDown(d, p));
+
+        d = 396d * 2.32d; p = 2;
+        assertEquals("roundDown ", 918.72d, MathX.roundDown(d, p));
+
         d = 0; p = 0;
         assertEquals("roundDown ", 0, MathX.roundDown(d, p));
         
@@ -753,25 +759,25 @@
         assertEquals("roundDown ", 100, MathX.roundDown(d, p));
         
         d = 0.049999999999999975d; p = 2;
-        assertEquals("round ", 0.04d, MathX.roundDown(d, p));
+        assertEquals("roundDown ", 0.05d, MathX.roundDown(d, p));
 
         d = 0.049999999999999975d; p = 1;
-        assertEquals("round ", 0.0d, MathX.roundDown(d, p));
+        assertEquals("roundDown ", 0.0d, MathX.roundDown(d, p));
         
         d = Double.NaN; p = 1;
-        assertEquals("round ", Double.NaN, MathX.roundDown(d, p));
+        assertEquals("roundDown ", Double.NaN, MathX.roundDown(d, p));
 
         d = Double.POSITIVE_INFINITY; p = 1;
-        assertEquals("round ", Double.NaN, MathX.roundDown(d, p));
+        assertEquals("roundDown ", Double.NaN, MathX.roundDown(d, p));
 
         d = Double.NEGATIVE_INFINITY; p = 1;
-        assertEquals("round ", Double.NaN, MathX.roundDown(d, p));
+        assertEquals("roundDown ", Double.NaN, MathX.roundDown(d, p));
 
         d = Double.MAX_VALUE; p = 1;
-        assertEquals("round ", Double.MAX_VALUE, MathX.roundDown(d, p));
+        assertEquals("roundDown ", Double.MAX_VALUE, MathX.roundDown(d, p));
 
         d = Double.MIN_VALUE; p = 1;
-        assertEquals("round ", 0.0d, MathX.roundDown(d, p));
+        assertEquals("roundDown ", 0.0d, MathX.roundDown(d, p));
     }
 
     public void testRoundUp() {
Index: test-data/spreadsheet/FormulaEvalTestData.xls
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