diff --git a/1ano/2semestre/poo/src/aula03/Grades.java b/1ano/2semestre/poo/src/aula03/Grades.java
index 0407fbb..4af54d7 100644
--- a/1ano/2semestre/poo/src/aula03/Grades.java
+++ b/1ano/2semestre/poo/src/aula03/Grades.java
@@ -31,16 +31,16 @@ public class Grades {
             System.out.printf("%5.1f  %5.1f  %5d\n", student.notaT, student.notaP, student.notaFinal);
         }
     }
-}
 
-class Student {
-    public double notaT;
-    public double notaP;
-    public int notaFinal;
+    private static class Student {
+        public double notaT;
+        public double notaP;
+        public int notaFinal;
 
-    public Student(double notaT, double notaP) {
-        this.notaT = notaT;
-        this.notaP = notaP;
-        this.notaFinal = (notaT < 7 || notaP < 7) ? 66 : (int) Math.round(0.4 * notaT + 0.6 * notaP);
+        public Student(double notaT, double notaP) {
+            this.notaT = notaT;
+            this.notaP = notaP;
+            this.notaFinal = (notaT < 7 || notaP < 7) ? 66 : (int) Math.round(0.4 * notaT + 0.6 * notaP);
+        }
     }
 }
diff --git a/1ano/2semestre/poo/src/aula03/PrimesSum.java b/1ano/2semestre/poo/src/aula03/PrimesSum.java
index 13425ad..b93a897 100644
--- a/1ano/2semestre/poo/src/aula03/PrimesSum.java
+++ b/1ano/2semestre/poo/src/aula03/PrimesSum.java
@@ -1,5 +1,6 @@
 package aula03;
 
+import utils.MathTools;
 import utils.UserInput;
 import java.util.Scanner;
 
@@ -14,20 +15,11 @@ public class PrimesSum {
 
         int sum = 0;
         for (int i = 0; i <= n; i++)
-            if (isNumPrime(i))
+            if (MathTools.isNumPrime(i))
                 sum += i;
 
         System.out.printf("A soma dos números primos até %d é %d\n", n, sum);
 
         sin.close();
     }
-
-    private static boolean isNumPrime(int n) {
-        if (n == 1)
-            return false;
-        for (int i = 2; i < n; i++)
-            if (n % i == 0)
-                return false;
-        return true;
-    }
 }
diff --git a/1ano/2semestre/poo/src/utils/MathTools.java b/1ano/2semestre/poo/src/utils/MathTools.java
index fa7c389..8744e9b 100644
--- a/1ano/2semestre/poo/src/utils/MathTools.java
+++ b/1ano/2semestre/poo/src/utils/MathTools.java
@@ -1,7 +1,23 @@
 package utils;
 
+import java.util.Random;
+
 public class MathTools {
     public static double round(double n, int places) {
         return (Math.round(n * Math.pow(10, places))) / Math.pow(10, places);
     }
+
+    public static double random(double minLimit, double maxLimit) {
+        Random rand = new Random();
+        return rand.nextDouble(minLimit, maxLimit);
+    }
+
+    public static boolean isNumPrime(int n) {
+        if (n <= 1)
+            return false;
+        for (int i = 2; i < n; i++)
+            if (n % i == 0)
+                return false;
+        return true;
+    }
 }