diff --git a/.obsidian/workspace.json b/.obsidian/workspace.json
index 3421ffb..bbe00b4 100644
--- a/.obsidian/workspace.json
+++ b/.obsidian/workspace.json
@@ -13,7 +13,7 @@
             "state": {
               "type": "markdown",
               "state": {
-                "file": "Algo/Séminaire/Chapter 5 - Recursivity.md",
+                "file": "Algo/Séminaire/Exercices seminaire.md",
                 "mode": "source",
                 "source": false
               }
@@ -85,7 +85,7 @@
             "state": {
               "type": "backlink",
               "state": {
-                "file": "Algo/Séminaire/Chapter 5 - Recursivity.md",
+                "file": "Algo/Séminaire/Exercices seminaire.md",
                 "collapseAll": false,
                 "extraContext": false,
                 "sortOrder": "alphabetical",
@@ -102,7 +102,7 @@
             "state": {
               "type": "outgoing-link",
               "state": {
-                "file": "Algo/Séminaire/Chapter 5 - Recursivity.md",
+                "file": "Algo/Séminaire/Exercices seminaire.md",
                 "linksCollapsed": false,
                 "unlinkedCollapsed": true
               }
@@ -125,7 +125,7 @@
             "state": {
               "type": "outline",
               "state": {
-                "file": "Algo/Séminaire/Chapter 5 - Recursivity.md"
+                "file": "Algo/Séminaire/Exercices seminaire.md"
               }
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           },
@@ -158,19 +158,19 @@
   },
   "active": "0d2d422aa24bb900",
   "lastOpenFiles": [
-    "Algo/Séminaire/Chapter 4 - A bit of imperative.md",
-    "Algo/Séminaire/Chapter 3 - Case analysis.md",
+    "Algo/Séminaire/Introduction.md",
     "Algo/Séminaire/Chapter 2 - Functions.md",
-    "Algo/Séminaire/Chapter 1 - CAML basics.md",
+    "Algo/Séminaire/Chapter 3 - Case analysis.md",
+    "Algo/Séminaire/Exercices seminaire.md",
     "Algo/Séminaire/Chapter 5 - Recursivity.md",
+    "Algo/Séminaire/Chapter 4 - A bit of imperative.md",
+    "Algo/Séminaire/Chapter 1 - CAML basics.md",
     "Algo/Séminaire/assets/exception-meme.png",
     "Algo/Séminaire/assets/filter-meme.png",
     "Algo/Séminaire/assets/if-meme.png",
-    "Algo/Séminaire/Exercices seminaire.md",
     "Algo/Séminaire/assets/basics-meme.png",
     "Algo/Séminaire/assets/functions-meme.jpg",
     "Algo/Séminaire/assets/unitaire-meme.png",
-    "Algo/Séminaire/Introduction.md",
     "Algo/Séminaire/assets/fact function response.png",
     "Algo/Séminaire/assets/recursivite-meme.png",
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diff --git a/Algo/Séminaire/Exercices seminaire.md b/Algo/Séminaire/Exercices seminaire.md
index 35ba844..8390611 100644
--- a/Algo/Séminaire/Exercices seminaire.md	
+++ b/Algo/Séminaire/Exercices seminaire.md	
@@ -305,3 +305,40 @@ let rec quo a b =
 	else 
 		1 + quo (a-b) b ;;
 ```
+
+## Exercise 4.9
+```Ocaml
+let rec reverse n = 
+	let str_n = string_of_int n in 
+	let len = String.length str_n in 
+	let rec reverse_helper index = 
+		if index < 0 then 
+			"" 
+		else 
+			String.make 1 str_n.[index] ^ reverse_helper (index - 1) 
+	in 
+	reverse_helper (len - 1) ;;
+
+let rec reverse_int n = 
+	let rec reverse_helper acc remaining = 
+	if remaining = 0 then 
+		acc 
+	else 
+		let last_digit = remaining mod 10 in 
+		let new_acc = acc * 10 + last_digit in 
+		let new_remaining = remaining / 10 
+	in reverse_helper new_acc new_remaining in reverse_helper 0 n ;;
+
+```
+
+## Exercise 4.10
+
+```Ocaml
+let rec multiply x y =
+  if x = 0 || y = 0 then
+    0
+  else if x mod 2 = 0 then
+    multiply (x / 2) (y * 2)
+  else
+    y + multiply (x / 2) (y * 2)
+```