# Need recursion challenge breakdown help?

Tell us what’s happening:
Describe your issue in detail here.
In the text explaination of the challenge I don’t understand where how they evaluated the function. How did they come up with, multiply(arr, n) == multiply(arr, n - 1) * arr[n - 1] from,

`````` function multiply(arr, n) {
let product = 1;
for (let i = 0; i < n; i++) {
product *= arr[i];
}
return product;
}
``````
``````  **Your code so far**
``````
``````
function sum(arr, n) {
// Only change code below this line

// Only change code above this line
}
//1 x n (stops when the index of arr is less than n)
//[4,6,8,6]
/* 1 * where n is first element so means i has to be less than 1

``````
``````  **Your browser information:**
``````

User Agent is: `Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/96.0.4664.110 Safari/537.36`

Challenge: Replace Loops using Recursion

The relationship `multiply(arr, n) == multiply(arr, n - 1) * arr[n - 1]` is saying that "the product of the first `n` elements of `arr`" is the same thing as "the product of the first `n-1` elements of `arr`" multiplied by "the `n`th element of `arr`".
The “big idea” with recursion is that the problem is broken down into a smaller version. In this case, multiply `n` elements of `arr` is replaced with the easier task of "multiply `n-1` elements of `arr`" until we get to the “base case” of "multiply `0` elements of `arr`".