diff --git a/labs/02-recursion-exercises.ipynb b/labs/02-recursion-exercises.ipynb
index 4c3ae444fda3964e7c9ffcdcf6f1e157ad2988de..b1cb714465394a51645766107f98a8b0fde51c24 100644
--- a/labs/02-recursion-exercises.ipynb
+++ b/labs/02-recursion-exercises.ipynb
@@ -2,7 +2,7 @@
  "cells": [
   {
    "cell_type": "markdown",
-   "id": "386bb47e",
+   "id": "61ded096",
    "metadata": {},
    "source": [
     "NAME:"
@@ -43,7 +43,32 @@
     "For each of the following questions:\n",
     "- In the `# YOUR CODE HERE` cell, remove `raise NotImplementedError()` to write your code\n",
     "- Write an example of use of your code or make sure the given examples and tests pass\n",
-    "- Add extra tests in the `#Tests` cell"
+    "- Add extra tests in the `#Tests` cell\n",
+    "\n",
+    "Recall on recursion:\n",
+    "\n",
+    "- Find a base case to stop the recursion\n",
+    "- Fin a decomposition of the problem to reach it\n",
+    "- Don't reach the Python recursion limits or infinite loops\n",
+    "\n",
+    "To compare iterative and recursive functions you may use the following time comparison functions:"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "id": "f6c23281-9c3d-488a-acb9-069964faff4b",
+   "metadata": {
+    "tags": []
+   },
+   "outputs": [],
+   "source": [
+    "import time\n",
+    "t1 = time.time()\n",
+    "# YOUR CODE\n",
+    "time.sleep(1)\n",
+    "dt = time.time() - t1\n",
+    "print(f\"Elapsed time: {dt:.4f} seconds\")"
    ]
   },
   {
@@ -683,7 +708,7 @@
     "editable": false,
     "nbgrader": {
      "cell_type": "code",
-     "checksum": "6af4501cee439c4fc21ff5b23ac801fe",
+     "checksum": "34e9dc5de2d87132b4fccc04281e1faf",
      "grade": true,
      "grade_id": "correct_annagram_rec",
      "locked": true,
@@ -701,7 +726,8 @@
     "assert palindrom_rec(\"AA\")\n",
     "assert not palindrom_rec(\"ABC\")\n",
     "assert palindrom_rec(\"ABA\")\n",
-    "assert palindrom_rec(\"LAVAL\")"
+    "assert palindrom_rec(\"LAVAL\")\n",
+    "assert palindrom_rec(\"toto\") == False"
    ]
   },
   {
@@ -1023,14 +1049,14 @@
     "tags": []
    },
    "source": [
-    "## Exercise 11: 2D Binary search\n",
+    "### Exercise 11: 2D Binary search\n",
     "\n",
     "We want to search for a target value in a 2D matrix where:\n",
     "\n",
     "- Each row is sorted in ascending order.\n",
     "- The first element of each row is greater than the last element of the previous row.\n",
     "\n",
-    "Implement a recursive function adn"
+    "Implement a recursive function to solve this problem (hint: use a similar approach to binary search in a 1D array)."
    ]
   },
   {
@@ -1101,14 +1127,6 @@
     "assert binary_search_2D(m, 11) == True\n",
     "assert binary_search_2D(m, 15) == False"
    ]
-  },
-  {
-   "cell_type": "code",
-   "execution_count": null,
-   "id": "34fea954-1cf6-4721-9d83-4504ca6e9901",
-   "metadata": {},
-   "outputs": [],
-   "source": []
   }
  ],
  "metadata": {