diff --git a/.github/workflows/mypy.yml b/.github/workflows/mypy.yml
new file mode 100644
index 000000000000..78badf82b586
--- /dev/null
+++ b/.github/workflows/mypy.yml
@@ -0,0 +1,26 @@
+name: mypy
+
+on: [push, pull_request]
+
+jobs:
+  mypy:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v2
+      - run: python3 -m pip install mypy
+      # FIXME: #4052 fix mypy errors in other directories and add them here
+      - run: python3 -m  mypy --ignore-missing-imports
+          arithmetic_analysis
+          backtracking
+          bit_manipulation
+          blockchain
+          boolean_algebra
+          cellular_automata
+          computer_vision
+          digital_image_processing
+          fuzzy_logic
+          genetic_algorithm
+          geodesy
+          knapsack
+          networking_flow
+          scheduling sorts
diff --git a/DIRECTORY.md b/DIRECTORY.md
index dfb673dea829..136825e41976 100644
--- a/DIRECTORY.md
+++ b/DIRECTORY.md
@@ -472,6 +472,7 @@
   * [Runge Kutta](https://github.com/TheAlgorithms/Python/blob/master/maths/runge_kutta.py)
   * [Segmented Sieve](https://github.com/TheAlgorithms/Python/blob/master/maths/segmented_sieve.py)
   * Series
+    * [Arithmetic Mean](https://github.com/TheAlgorithms/Python/blob/master/maths/series/arithmetic_mean.py)
     * [Geometric Mean](https://github.com/TheAlgorithms/Python/blob/master/maths/series/geometric_mean.py)
     * [Geometric Series](https://github.com/TheAlgorithms/Python/blob/master/maths/series/geometric_series.py)
     * [Harmonic Series](https://github.com/TheAlgorithms/Python/blob/master/maths/series/harmonic_series.py)