diff --git a/docs/1-trial-session/10-loop/_samples/product-alt/index.html b/docs/1-trial-session/10-loop/_samples/product-alt/index.html
deleted file mode 100644
index 07ea1c3a0..000000000
--- a/docs/1-trial-session/10-loop/_samples/product-alt/index.html
+++ /dev/null
@@ -1,10 +0,0 @@
-
-
-
-
- 積の演習の解答例 (複合代入演算子)
-
-
-
-
-
diff --git a/docs/1-trial-session/10-loop/_samples/product-alt/script.js b/docs/1-trial-session/10-loop/_samples/product-alt/script.js
deleted file mode 100644
index a13270ea7..000000000
--- a/docs/1-trial-session/10-loop/_samples/product-alt/script.js
+++ /dev/null
@@ -1,5 +0,0 @@
-let product = 1;
-for (let i = 1; i <= 10; i += 1) {
- product *= i;
-}
-document.write(product);
diff --git a/docs/1-trial-session/10-loop/_samples/product/script.js b/docs/1-trial-session/10-loop/_samples/product/script.js
index 67818e7a7..a13270ea7 100644
--- a/docs/1-trial-session/10-loop/_samples/product/script.js
+++ b/docs/1-trial-session/10-loop/_samples/product/script.js
@@ -1,5 +1,5 @@
let product = 1;
-for (let i = 1; i <= 10; i = i + 1) {
- product = product * i;
+for (let i = 1; i <= 10; i += 1) {
+ product *= i;
}
document.write(product);
diff --git a/docs/1-trial-session/10-loop/index.mdx b/docs/1-trial-session/10-loop/index.mdx
index 3f5f8f2c7..a950e25b6 100644
--- a/docs/1-trial-session/10-loop/index.mdx
+++ b/docs/1-trial-session/10-loop/index.mdx
@@ -141,20 +141,6 @@ const string2 = `10から2を引くと${10 - 2}です。`;
-```javascript
-let product = 1;
-for (let i = 1; i <= 10; i = i + 1) {
- product = product * i;
-}
-document.write(product);
-```
-
-
-
-別解
-
-複合代入演算子を使うと次のようにも書けます。
-
```javascript
let product = 1;
for (let i = 1; i <= 10; i += 1) {
@@ -163,7 +149,7 @@ for (let i = 1; i <= 10; i += 1) {
document.write(product);
```
-
+