# Weighted average

JavaScript, Math · Nov 3, 2020

Calculates the weighted average of two or more numbers.

- Use
`Array.prototype.reduce()`

to create the weighted sum of the values and the sum of the weights. - Divide them with each other to get the weighted average.

```
const weightedAverage = (nums, weights) => {
const [sum, weightSum] = weights.reduce(
(acc, w, i) => {
acc[0] = acc[0] + nums[i] * w;
acc[1] = acc[1] + w;
return acc;
},
[0, 0]
);
return sum / weightSum;
};
```

`weightedAverage([1, 2, 3], [0.6, 0.2, 0.3]); // 1.72727`