Hey @Christiaan_Huizer,

Strictly speaking, itâ€™s not â€śmultiplicationâ€ť (because that would make an N x N matrix) but more of â€śmaskingâ€ť.

The logic here is to multiply Nth element of the first list by the Nth element of the second list. Which means you still have to iterate (i.e. perform the same operation once per list item) but instead of iterating on items themselves you should iterate on indices `1, 2, 3 ... List.Count()`

so that you can use the same index on both list to extract corresponding values:

```
Sequence(1, thisRow.transformed.Count()).FormulaMap(
thisRow.transformed.Nth(CurrentValue) * thisRow.[days per response].Nth(CurrentValue)
)
```

Here Iâ€™m making another list thatâ€™s a sequence of numbers from 1 to `transformed.Count()`

and then Iâ€™m using items in this list (numbers from 1 to last) to get `.Nth()`

element of each list and multiply them to produce Nth element of a resulting list.

I implemented this in your doc. Btw, no need to use `ListCombine()`

there â€” simply use `List()`

to create a list of elements that you enumerate as function parameters. Also no need to `ListCombine()`

on a column â€” you can simply reference that column (see Input 2 / Days per response column)