diff --git a/module2/exo1/toy_notebook_en.ipynb b/module2/exo1/toy_notebook_en.ipynb
index d899856101161ff2c1a8adb15b924fb5348b12e4..1579bcca729243ec964cf76b0efe618f71ea171d 100644
--- a/module2/exo1/toy_notebook_en.ipynb
+++ b/module2/exo1/toy_notebook_en.ipynb
@@ -40,7 +40,7 @@
     "hidePrompt": false
    },
    "source": [
-    "## Buffon's needle\n",
+    "## 1.2 Buffon's needle\n",
     "Applying the method of [Buffon's needle](https://en.wikipedia.org/wiki/Buffon%27s_needle_problem), we get the __approximation__"
    ]
   },
@@ -79,7 +79,7 @@
     "hidePrompt": false
    },
    "source": [
-    "## Using a surface fraction argument\n",
+    "## 1.3 Using a surface fraction argument\n",
     "A method that is easier to understand and does not make use of the $\\sin$ function is based on the fact that if $X\\sim U(0,1)$ and $Y\\sim U(0,1)$, then $P[X^2+Y^2\\leq 1] = \\pi/4$ (see [\"Monte Carlo method\" on Wikipedia](https://en.wikipedia.org/wiki/Monte_Carlo_method)). The following code uses this approach:"
    ]
   },