We already noted that ‘array’ is our selected range when using ‘INDEX’.
The first thing we want to look at is a situation where the ‘column_num’ is optional.
This can only be the case when we select an array range that consists of a single column such as B3:B6 (the column for 1 box in our example scenario).
In this case the row number is required.
Practically speaking, we are interested in what our price would be for a box of 500 products if we were to purchase just a single box.
So when we type ‘=INDEX(B3:B6,B9)’ in a cell (C9 in the figure below), our returned value should be $245.00.
Note that in this example we have referenced B9 for our row number which is the value 3. You would get the same result if you replaced B9 in the ‘row_num’ parameter with the actual value 3.