diff --git a/snippets/average_by.md b/snippets/average_by.md
new file mode 100644
index 000000000..f88fd9667
--- /dev/null
+++ b/snippets/average_by.md
@@ -0,0 +1,18 @@
+---
+title: average_by
+tags: math,list,function,intermediate
+---
+
+Returns the average of a list, after mapping each element to a value using the provided function.
+
+Use `map()` to map each element to the value returned by `fn`.
+Use `sum()` to sum all of the mapped values, divide by `len(lst)`.
+
+```py
+def average_by(lst, fn=lambda x: x):
+  return sum(map(fn, lst), 0.0) / len(lst)
+```
+
+```py
+average_by([{ 'n': 4 }, { 'n': 2 }, { 'n': 8 }, { 'n': 6 }], lambda x: x['n']) # 5.0
+```