diff --git a/src/problem/mod.rs b/src/problem/mod.rs
index f4c7c94..33f2902 100644
--- a/src/problem/mod.rs
+++ b/src/problem/mod.rs
@@ -570,3 +570,5 @@ mod p2716_minimize_string_length;
 mod p2360_longest_cycle_in_a_graph;
 
 mod p2109_adding_spaces_to_a_string;
+
+mod p2278_percentage_of_letter_in_string;
diff --git a/src/problem/p2278_percentage_of_letter_in_string.rs b/src/problem/p2278_percentage_of_letter_in_string.rs
new file mode 100644
index 0000000..5b27b71
--- /dev/null
+++ b/src/problem/p2278_percentage_of_letter_in_string.rs
@@ -0,0 +1,25 @@
+/**
+ * [2278] Percentage of Letter in String
+ */
+pub struct Solution {}
+
+// submission codes start here
+
+impl Solution {
+    pub fn percentage_letter(s: String, letter: char) -> i32 {
+        (s.chars().filter(|c| *c == letter).count() * 100 / s.len()) as i32
+    }
+}
+
+// submission codes end
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_2278() {
+        assert_eq!(33, Solution::percentage_letter("foobar".to_owned(), 'o'));
+        assert_eq!(0, Solution::percentage_letter("jjjj".to_owned(), 'k'));
+    }
+}