All units implemented two operator overloads that did not really make sense.

Changed this for all units.
Updated tests.

Example 1:
Force operator *(Force left, Force right);

What is the result of multiplying two forces? Although it can be done, I don't see the need for it and will remove it until a need is found.

Example 2:
-        public static Force operator /(Force left, Force right)
+        public static double operator /(Force left, Force right)

The result of dividing one force with another should be the ratio, not a new force.

Author: angularsen

Src/UnitsNet/Force.cs

@@ -144,11 +144,6 @@ public static Force FromMassAcceleration(Mass mass, double metersPerSecondSquare
             return new Force(left.Newtons - right.Newtons);
         }
 
-        public static Force operator *(Force left, Force right)
-        {
-            return new Force(left.Newtons*right.Newtons);
-        }
-
         public static Force operator *(double left, Force right)
         {
             return new Force(left*right.Newtons);
@@ -164,9 +159,9 @@ public static Force FromMassAcceleration(Mass mass, double metersPerSecondSquare
             return new Force(left.Newtons/right);
         }
 
-        public static Force operator /(Force left, Force right)
+        public static double operator /(Force left, Force right)
         {
-            return new Force(left.Newtons/right.Newtons);
+            return left.Newtons/right.Newtons;
         }
 
         #endregion

Src/UnitsNet/Length.cs

@@ -199,19 +199,14 @@ public static Length FromNanometers(double nm)
             return FromMeters(left.Meters*right);
         }
 
-        public static Length operator *(Length left, Length right)
-        {
-            return FromMeters(left.Meters*right.Meters);
-        }
-
         public static Length operator /(Length left, double right)
         {
             return FromMeters(left.Meters/right);
         }
 
-        public static Length operator /(Length left, Length right)
+        public static double operator /(Length left, Length right)
         {
-            return FromMeters(left.Meters/right.Meters);
+            return left.Meters/right.Meters;
         }
 
         #endregion

Src/UnitsNet/Length2d.cs

@@ -213,11 +213,11 @@ public static Length2d FromMillimeters(double xMillimeters, double yMillimeters)
             return FromMeters(x, y);
         }
 
-        public static Length2d operator /(Length2d left, Length2d right)
+        public static Vector2 operator /(Length2d left, Length2d right)
         {
             double x = left.X.Meters/right.X.Meters;
             double y = left.Y.Meters/right.Y.Meters;
-            return FromMeters(x, y);
+            return new Vector2(x, y);
         }
 
         #endregion

Src/UnitsNet/Mass.cs

@@ -237,14 +237,9 @@ public static Mass FromShortTons(double value)
             return new Mass(left*right.Kilograms);
         }
 
-        public static Mass operator *(Mass left, Mass right)
+        public static double operator /(Mass left, Mass right)
         {
-            return new Mass(left.Kilograms*right.Kilograms);
-        }
-
-        public static Mass operator /(Mass left, Mass right)
-        {
-            return new Mass(left.Kilograms/right.Kilograms);
+            return left.Kilograms/right.Kilograms;
         }
 
         public static Mass operator /(Mass left, double right)

Src/UnitsNet/Pressure.cs

@@ -206,19 +206,14 @@ public static Pressure FromPsi(double psi)
             return new Pressure(left*right.Pascals);
         }
 
-        public static Pressure operator *(Pressure left, Pressure right)
-        {
-            return new Pressure(left.Pascals*right.Pascals);
-        }
-
         public static Pressure operator /(Pressure left, double right)
         {
             return new Pressure(left.Pascals/right);
         }
 
-        public static Pressure operator /(Pressure left, Pressure right)
+        public static double operator /(Pressure left, Pressure right)
         {
-            return new Pressure(left.Pascals/right.Pascals);
+            return left.Pascals/right.Pascals;
         }
 
         #endregion

Tests/ForceTests.cs

@@ -42,11 +42,10 @@ public void ArithmeticOperators()
             Assert.AreEqual(1, (Force.FromNewtons(2) - newton).Newtons, Delta);
             Assert.AreEqual(2, (newton + newton).Newtons, Delta);
             Assert.AreEqual(1, (Force.FromNewtons(2) - newton).Newtons, Delta);
-            Assert.AreEqual(10, (newton*Force.FromNewtons(10)).Newtons, Delta);
             Assert.AreEqual(10, (newton*10).Newtons, Delta);
             Assert.AreEqual(10, (10*newton).Newtons, Delta);
             Assert.AreEqual(2, (Force.FromNewtons(10)/5).Newtons, Delta);
-            Assert.AreEqual(2, (Force.FromNewtons(10)/Force.FromNewtons(5)).Newtons, Delta);
+            Assert.AreEqual(2, Force.FromNewtons(10)/Force.FromNewtons(5), Delta);
         }
 
         [Test]

Tests/Length2dTests.cs

@@ -73,8 +73,8 @@ public void ArithmeticOperators()
             Assert.AreEqual(4, (Length2d.FromMeters(2, 2)*v).Meters.Y, Delta);
             Assert.AreEqual(2, (Length2d.FromMeters(10, 20)/5).Meters.X, Delta);
             Assert.AreEqual(4, (Length2d.FromMeters(10, 20)/5).Meters.Y, Delta);
-            Assert.AreEqual(2, (Length2d.FromMeters(10, 20)/Length2d.FromMeters(5, 5)).Meters.X, Delta);
-            Assert.AreEqual(4, (Length2d.FromMeters(10, 20)/Length2d.FromMeters(5, 5)).Meters.Y, Delta);
+            Assert.AreEqual(2, (Length2d.FromMeters(10, 20)/Length2d.FromMeters(5, 5)).X, Delta);
+            Assert.AreEqual(4, (Length2d.FromMeters(10, 20)/Length2d.FromMeters(5, 5)).Y, Delta);
         }
 
         [Test]

Tests/LengthTests.cs

@@ -55,9 +55,8 @@ public void ArithmeticOperators()
             Assert.AreEqual(2, (v + v).Meters, Delta);
             Assert.AreEqual(10, (v*10).Meters, Delta);
             Assert.AreEqual(10, (10*v).Meters, Delta);
-            Assert.AreEqual(2, (Length.FromMeters(2)*v).Meters, Delta);
             Assert.AreEqual(2, (Length.FromMeters(10)/5).Meters, Delta);
-            Assert.AreEqual(2, (Length.FromMeters(10)/Length.FromMeters(5)).Meters, Delta);
+            Assert.AreEqual(2, Length.FromMeters(10)/Length.FromMeters(5), Delta);
         }
 
         [Test]

Tests/MassTests.cs

@@ -56,9 +56,8 @@ public void ArithmeticOperators()
             Assert.AreEqual(2, (v + v).Kilograms, Delta);
             Assert.AreEqual(10, (v*10).Kilograms, Delta);
             Assert.AreEqual(10, (10*v).Kilograms, Delta);
-            Assert.AreEqual(2, (Mass.FromKilograms(2)*v).Kilograms, Delta);
             Assert.AreEqual(2, (Mass.FromKilograms(10)/5).Kilograms, Delta);
-            Assert.AreEqual(2, (Mass.FromKilograms(10)/Mass.FromKilograms(5)).Kilograms, Delta);
+            Assert.AreEqual(2, Mass.FromKilograms(10)/Mass.FromKilograms(5), Delta);
         }
 
         [Test]

Tests/PressureTests.cs

@@ -52,9 +52,8 @@ public void ArithmeticOperators()
             Assert.AreEqual(2, (v + v).Pascals, Delta);
             Assert.AreEqual(10, (v*10).Pascals, Delta);
             Assert.AreEqual(10, (10*v).Pascals, Delta);
-            Assert.AreEqual(2, (Pressure.FromPascals(2)*v).Pascals, Delta);
             Assert.AreEqual(2, (Pressure.FromPascals(10)/5).Pascals, Delta);
-            Assert.AreEqual(2, (Pressure.FromPascals(10)/Pressure.FromPascals(5)).Pascals, Delta);
+            Assert.AreEqual(2, Pressure.FromPascals(10)/Pressure.FromPascals(5), Delta);
         }
 
         [Test]