diff --git a/main/NPOI.Core.csproj b/main/NPOI.Core.csproj
index bed446fb1..7609abefb 100644
--- a/main/NPOI.Core.csproj
+++ b/main/NPOI.Core.csproj
@@ -15,7 +15,7 @@
 
   <ItemGroup>
     <PackageReference Include="Enums.NET" Version="4.0.1" />
-    <PackageReference Include="ExtendedNumerics.BigDecimal" Version="2023.1000.4.35" />
+    <PackageReference Include="ExtendedNumerics.BigDecimal" Version="2025.1000.2.122" />
     <PackageReference Include="MathNet.Numerics.Signed" Version="5.0.0" />
     <PackageReference Include="Microsoft.IO.RecyclableMemoryStream" Version="3.0.0" />
     <PackageReference Include="BouncyCastle.Cryptography" Version="2.3.0" />
diff --git a/main/SS/Formula/Functions/MathX.cs b/main/SS/Formula/Functions/MathX.cs
index b7639e477..47123d2ea 100644
--- a/main/SS/Formula/Functions/MathX.cs
+++ b/main/SS/Formula/Functions/MathX.cs
@@ -170,13 +170,8 @@ public static double RoundDown(double n, int p)
             {
                 if(p != 0)
                 {
-                    var temp = BigDecimal.Pow(10, p);
                     var value = new BigDecimal(n);
-                    var absValue = BigDecimal.Abs(value);
-                    var multValue = BigDecimal.Multiply(absValue, temp);
-                    var roundingValue = BigDecimal.Subtract(multValue, new BigDecimal(0.5));
-                    var roundedValue = BigDecimal.Round(roundingValue, MidpointRounding.AwayFromZero);
-                    retval = Sign(n) * ((double)BigDecimal.Divide(roundedValue, temp));
+                    retval = (double)BigDecimal.Round(value, p);
                 }
                 else
                 {
diff --git a/testcases/main/SS/Formula/Functions/TestMathX.cs b/testcases/main/SS/Formula/Functions/TestMathX.cs
index 1d814b086..c0ab72406 100644
--- a/testcases/main/SS/Formula/Functions/TestMathX.cs
+++ b/testcases/main/SS/Formula/Functions/TestMathX.cs
@@ -811,7 +811,7 @@ public void TestRoundDown()
             d = Double.MinValue; p = 1;
             AssertEquals("roundDown ", 0.0d, MathX.RoundDown(d, p));
 
-            d = 17.56;
+            d = 17.56; p = 2;
             AssertEquals("roundDown ", 17.56, MathX.RoundDown(d, p));
         }
         [Test]