Create weighted_average.md

snippets/weighted_average.md

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+---
+title: weighted_average
+tags: list,intermediate
+---
+
+Returns the weighted average of two or more noumbers.
+
+- Use `sum` to sum the products of the numbers by it's weight and to sum the weights.
+- Use `for i in range(len(nums))` to move over every number in the two lists.
+
+```py
+def weightedAverage(nums,weights):
+    return sum(nums[i] * weights[i] for i in range(len(nums))) / sum(weights)
+```
+
+```py
+weightedAverage([1, 2, 3], [0.6,0.2,0.3]) # 1.727272727272727
+```