diff --git a/problem01/problem01.js b/problem01/problem01.js
index 4bee421..8c84cec 100644
--- a/problem01/problem01.js
+++ b/problem01/problem01.js
@@ -10,13 +10,13 @@ function grade(score) {
   let result;
 
   if (score > 100 || score < 0) {
-    result = "C"; // 🚨
+    result = "Invalid";
   } else if (score >= 90) {
-    result = "B"; // 🚨
-  } else if (score >= 80) {
-    result = "A"; // 🚨
+    result = "A";
+  } else if (score >= 85) {
+    result = "B";
   } else {
-    result = "B"; // 🚨
+    result = "C";
   }
 
   return result;
diff --git a/problem02/problem02.js b/problem02/problem02.js
index ff7014b..b783196 100644
--- a/problem02/problem02.js
+++ b/problem02/problem02.js
@@ -9,16 +9,21 @@ function checkNumber(num) {
   let result;
 
   switch (true) {
-    case typeof num !== "number" || isNaN(num): // 🚨
+    case typeof num !== "number" || isNaN(num):
       result = "숫자가 아닙니다.";
-    case num > 0: // 🚨
+      break;
+    case num > 0:
       result = "양수입니다.";
-    case num < 0: // 🚨
+      break;
+    case num < 0:
       result = "음수입니다.";
-    case num === 0: // 🚨
+      break;
+    case num === 0:
       result = "0입니다.";
-    default: // 🚨
-      result = "알 수 없는 오류입니다.";
+      break;
+    default:
+      result = "숫자가 아닙니다.";
+      break;
   }
 
   return result;
diff --git a/problem03/problem03.js b/problem03/problem03.js
index 1b59f8c..d30d842 100644
--- a/problem03/problem03.js
+++ b/problem03/problem03.js
@@ -7,10 +7,10 @@
  */
 /* problem03.js */
 function sumExcludingMultiplesOfThreeAndFive(n) {
-  let sum = 1; // 🚨
+  let sum = 0;
   for (let i = 1; i <= n; i++) {
-    if (i % 3 !== 0 && i % 5 !== 0) continue; // 🚨
-    sum -= i; // 🚨
+    if (i % 3 == 0 || i % 5 == 0) continue;
+    sum += i;
   }
   return sum;
 }
diff --git a/problem04/problem04.js b/problem04/problem04.js
index 0c25c97..6dc8905 100644
--- a/problem04/problem04.js
+++ b/problem04/problem04.js
@@ -6,12 +6,12 @@
  * - 현재 코드는 잘못된 로직으로 인해 테스트가 실패합니다.
  */
 function sumUpToTen(n) {
-  let sum = 1; // 🚨
+  let sum = 0;
   let i = 1;
 
   while (i <= n) {
-    if (i > 10) break; // 🚨
-    sum -= i; // 🚨
+    if (i > 10) break;
+    sum += i;
     i++;
   }
 
diff --git a/problem05/problem05.js b/problem05/problem05.js
index c74abb6..4d48761 100644
--- a/problem05/problem05.js
+++ b/problem05/problem05.js
@@ -6,11 +6,11 @@
  * - 모든 조건을 확인한 후 최후에 `return`을 사용하세요.
  */
 function sumOfSmallProducts(n) {
-  let sum = 1; // 🚨
+  let sum = 0;
   for (let i = 1; i <= n; i++) {
     for (let j = 1; j <= n; j++) {
-      if (i * j > 10) continue; // 🚨
-      sum -= i * j; // 🚨
+      if (i * j > 10) continue;
+      sum += i * j;
     }
   }
   return sum;