diff --git a/1ano/2semestre/poo/src/aula11/ex2/Gradebook.java b/1ano/2semestre/poo/src/aula11/ex2/Gradebook.java
index 00867ed..5c2b05a 100644
--- a/1ano/2semestre/poo/src/aula11/ex2/Gradebook.java
+++ b/1ano/2semestre/poo/src/aula11/ex2/Gradebook.java
@@ -1,15 +1,14 @@
 package aula11.ex2;
 
-import utils.MathTools;
-
 import java.io.*;
 import java.nio.file.Files;
 import java.nio.file.Path;
 import java.nio.file.Paths;
 import java.util.*;
 
-public class Gradebook implements IGradeCalculator {
+public class Gradebook {
     private final LinkedList<Student> students = new LinkedList<>();
+    private final IGradeCalculator gradeCalculator = new SimpleGradeCalculator();
 
     public void load(String filename) {
         LinkedList<String> lines = new LinkedList<>();
@@ -42,16 +41,11 @@ public class Gradebook implements IGradeCalculator {
     }
 
     public double calculateAverageGrade(String name) {
-        return calculate(getStudent(name).getGrades());
-    }
-
-    @Override
-    public double calculate(LinkedList<Double> grades) {
-        return MathTools.media(grades);
+        return gradeCalculator.calculate(getStudent(name).getGrades());
     }
 
     public void printAllStudents() {
         for (Student student : students)
-            System.out.printf("Nome: %s%nNota Final: %.2f%n%n", student.getName(), calculate(student.getGrades()));
+            System.out.printf("Nome: %s%nNota Final: %.2f%n%n", student.getName(), gradeCalculator.calculate(student.getGrades()));
     }
 }
diff --git a/1ano/2semestre/poo/src/aula11/ex2/SimpleGradeCalculator.java b/1ano/2semestre/poo/src/aula11/ex2/SimpleGradeCalculator.java
new file mode 100644
index 0000000..7192ed8
--- /dev/null
+++ b/1ano/2semestre/poo/src/aula11/ex2/SimpleGradeCalculator.java
@@ -0,0 +1,13 @@
+package aula11.ex2;
+
+import java.util.LinkedList;
+
+public class SimpleGradeCalculator implements IGradeCalculator {
+    @Override
+    public double calculate(LinkedList<Double> grades) {
+        double sum = 0;
+        for (double n : grades)
+            sum += n;
+        return sum / grades.size();
+    }
+}