diff --git a/poincare/include/poincare/multiplication.h b/poincare/include/poincare/multiplication.h
index 256c1d479..cf16e64ba 100644
--- a/poincare/include/poincare/multiplication.h
+++ b/poincare/include/poincare/multiplication.h
@@ -63,10 +63,8 @@ private:
 };
 
 class Multiplication : public NAryExpression {
-  friend class AdditionNode;
   friend class Addition;
   friend class Power;
-  friend class UnitConvert;
 public:
   Multiplication(const MultiplicationNode * n) : NAryExpression(n) {}
   static Multiplication Builder(const Tuple & children = {}) { return TreeHandle::NAryBuilder<Multiplication, MultiplicationNode>(convert(children)); }
@@ -92,7 +90,6 @@ public:
 private:
   // Simplification
   Expression privateShallowReduce(ExpressionNode::ReductionContext reductionContext, bool expand, bool canBeInterrupted);
-  void mergeMultiplicationChildrenInPlace();
   void factorizeBase(int i, int j, ExpressionNode::ReductionContext reductionContext);
   void mergeInChildByFactorizingBase(int i, Expression e, ExpressionNode::ReductionContext reductionContext);
   void factorizeExponent(int i, int j, ExpressionNode::ReductionContext reductionContext);
diff --git a/poincare/include/poincare/n_ary_expression.h b/poincare/include/poincare/n_ary_expression.h
index 6db14d2ed..97455f3af 100644
--- a/poincare/include/poincare/n_ary_expression.h
+++ b/poincare/include/poincare/n_ary_expression.h
@@ -52,6 +52,7 @@ public:
   Expression squashUnaryHierarchyInPlace() {
     return node()->squashUnaryHierarchyInPlace();
   }
+  void mergeSameTypeChildrenInPlace();
   /* allChildrenAreReal returns:
    * - 1 if all children are real
    * - 0 if all non real children are ComplexCartesian
diff --git a/poincare/src/addition.cpp b/poincare/src/addition.cpp
index 02167bf56..9db97c40d 100644
--- a/poincare/src/addition.cpp
+++ b/poincare/src/addition.cpp
@@ -144,14 +144,7 @@ Expression Addition::shallowReduce(ExpressionNode::ReductionContext reductionCon
 
   /* Step 1: Addition is associative, so let's start by merging children which
    * are additions. */
-  int i = 0;
-  while (i < numberOfChildren()) {
-    if (childAtIndex(i).type() == ExpressionNode::Type::Addition) {
-      mergeChildrenAtIndexInPlace(childAtIndex(i), i);
-      continue;
-    }
-    i++;
-  }
+  mergeSameTypeChildrenInPlace();
 
   const int childrenCount = numberOfChildren();
   assert(childrenCount > 1);
@@ -230,7 +223,7 @@ Expression Addition::shallowReduce(ExpressionNode::ReductionContext reductionCon
 
   /* Step 5: Factorize like terms. Thanks to the simplification order, those are
    * next to each other at this point. */
-  i = 0;
+  int i = 0;
   while (i < numberOfChildren()-1) {
     Expression e1 = childAtIndex(i);
     Expression e2 = childAtIndex(i+1);
diff --git a/poincare/src/multiplication.cpp b/poincare/src/multiplication.cpp
index 38b9fd4e3..9a7fff846 100644
--- a/poincare/src/multiplication.cpp
+++ b/poincare/src/multiplication.cpp
@@ -481,7 +481,7 @@ Expression Multiplication::shallowBeautify(ExpressionNode::ReductionContext redu
       }
       // Build final Expression
       result = Multiplication::Builder(resultWithoutUnit, units);
-      static_cast<Multiplication &>(result).mergeMultiplicationChildrenInPlace();
+      static_cast<Multiplication &>(result).mergeSameTypeChildrenInPlace();
     }
   }
 
@@ -505,7 +505,7 @@ Expression Multiplication::privateShallowReduce(ExpressionNode::ReductionContext
 
   /* Step 1: MultiplicationNode is associative, so let's start by merging children
    * which also are multiplications themselves. */
-  mergeMultiplicationChildrenInPlace();
+  mergeSameTypeChildrenInPlace();
 
   Context * context = reductionContext.context();
 
@@ -790,19 +790,6 @@ Expression Multiplication::privateShallowReduce(ExpressionNode::ReductionContext
   return result;
 }
 
-void Multiplication::mergeMultiplicationChildrenInPlace() {
-  // Multiplication is associative: a*(b*c)->a*b*c
-  int i = 0;
-  while (i < numberOfChildren()) {
-    Expression c = childAtIndex(i);
-    if (c.type() == ExpressionNode::Type::Multiplication) {
-      mergeChildrenAtIndexInPlace(c, i);
-      continue;
-    }
-    i++;
-  }
-}
-
 void Multiplication::factorizeBase(int i, int j, ExpressionNode::ReductionContext reductionContext) {
   /* This function factorizes two children which have a common base. For example
    * if this is Multiplication::Builder(pi^2, pi^3), then pi^2 and pi^3 could be merged
diff --git a/poincare/src/n_ary_expression.cpp b/poincare/src/n_ary_expression.cpp
index 917877808..314f4b8cb 100644
--- a/poincare/src/n_ary_expression.cpp
+++ b/poincare/src/n_ary_expression.cpp
@@ -97,6 +97,21 @@ int NAryExpressionNode::simplificationOrderGreaterType(const ExpressionNode * e,
   return 0;
 }
 
+void NAryExpression::mergeSameTypeChildrenInPlace() {
+  // Multiplication is associative: a*(b*c)->a*b*c
+  // The same goes for Addition
+  ExpressionNode::Type parentType = type();
+  int i = 0;
+  while (i < numberOfChildren()) {
+    Expression c = childAtIndex(i);
+    if (c.type() != parentType) {
+      i++;
+    } else {
+      mergeChildrenAtIndexInPlace(c, i);
+    }
+  }
+}
+
 int NAryExpression::allChildrenAreReal(Context * context) const {
   int i = 0;
   int result = 1;
diff --git a/poincare/src/unit_convert.cpp b/poincare/src/unit_convert.cpp
index 0002bb500..a4d4fedd5 100644
--- a/poincare/src/unit_convert.cpp
+++ b/poincare/src/unit_convert.cpp
@@ -71,7 +71,7 @@ Expression UnitConvert::shallowReduce(ExpressionNode::ReductionContext reduction
     return Undefined::Builder();
   }
   division = Multiplication::Builder(Float<double>::Builder(floatValue), finalUnit);
-  static_cast<Multiplication &>(division).mergeMultiplicationChildrenInPlace();
+  static_cast<Multiplication &>(division).mergeSameTypeChildrenInPlace();
   replaceWithInPlace(division);
   return division;
 }