diff --git a/argorithm/balanced_array.py b/argorithm/balanced_array.py
new file mode 100644
index 0000000..4a383e8
--- /dev/null
+++ b/argorithm/balanced_array.py
@@ -0,0 +1,12 @@
+def balanced_sum(arr):
+    size = arr.pop(0)
+    for i in range(size):
+        # print('arr[:i+1]: ', arr[:i+1])
+        # print('arr[-(len(arr)-i):]: ', arr[-(len(arr)-i):])
+        if sum(arr[:i+1]) == sum(arr[-(len(arr)-i):]):
+            return i
+
+
+if __name__ == '__main__':
+    real_answer = balanced_sum([4, 1, 2, 3, 3])
+    print(real_answer)
diff --git a/argorithm/last_and_second-last.py b/argorithm/last_and_second-last.py
new file mode 100644
index 0000000..b2b630d
--- /dev/null
+++ b/argorithm/last_and_second-last.py
@@ -0,0 +1,8 @@
+def lastLetters(word):
+    str_to_list = list(word)[-2:]
+    return ' '.join(str_to_list[::-1])
+
+
+if __name__ == '__main__':
+    real_answer = lastLetters('bat')
+    print(real_answer)
diff --git a/argorithm/prime_or_not.py b/argorithm/prime_or_not.py
new file mode 100644
index 0000000..0a7b6ad
--- /dev/null
+++ b/argorithm/prime_or_not.py
@@ -0,0 +1,22 @@
+'''
+문제 :
+주어진 숫자가 소수 일 경우 1을 return
+소수가 아닐 경우 약수 중 1을 제외한 가장 작은 숫자 return
+
+아직 푸는중임!~!!!!
+'''
+
+def is_prime(n):
+    answer = []
+    for i in range(2, n):
+        if n % i == 0:
+            answer.append(i)
+            n = n//i
+        else:
+            return 1
+    return min(answer)
+
+
+if __name__ == '__main__':
+    real_answer = is_prime(24)
+    print(real_answer)