diff --git a/suhwan2004/Maximum Average Subarray I.js b/suhwan2004/Maximum Average Subarray I.js
new file mode 100644
index 0000000..c3d2723
--- /dev/null
+++ b/suhwan2004/Maximum Average Subarray I.js	
@@ -0,0 +1,26 @@
+/**
+ * @param {number[]} nums
+ * @param {number} k
+ * @return {number}
+ */
+
+/*
+
+17:55 ~ 18:17
+Time : O(N)
+Space : O(1)
+Algo : for
+Ds : X
+*/
+
+var findMaxAverage = function(nums, k) {
+    if(nums.length === 1) return nums[0]
+    if(k === 1) return Math.max(...nums)
+    
+    let sum = 0
+
+    return nums.reduce((prev, cur, i) => {
+        sum += cur - (i >= k ? nums[i-k] : 0)
+        return k-1 <= i ? Math.max(sum/k, prev) : prev
+    }, -Infinity)
+};
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