diff --git a/10-trait/10-01-trait.md b/10-trait/10-01-trait.md
index 28dd20b..73bce77 100644
--- a/10-trait/10-01-trait.md
+++ b/10-trait/10-01-trait.md
@@ -38,7 +38,7 @@ fn main() {
 这个程序会输出：
 
 ```
-circle c has an area of 1
+circle c has an area of 3.141592653589793
 ```
 
 ## trait与泛型