diff --git a/src/learn/04/index.md b/src/learn/04/index.md
index a915099..3ff6334 100644
--- a/src/learn/04/index.md
+++ b/src/learn/04/index.md
@@ -29,7 +29,7 @@ print("%.2f" % a)
 ```py
 a=10
 b=3
-print(".2f" % a/b) # 这里是错误的❌
+print("%.2f" % a/b) # 这里是错误的❌
 ```
 
 可以改成：