If we look at cell D82, we will notice that this cell is

currently calculating the total sales for the month of January by

doing a subtotal using a sum function on the January sales data.

This is also the case for the cells below,

cell D85, D88 and D91.

If we select all of these the sales,

we will notice that this column is a named range, labeled sales 2.

We will be using named ranges going forward.

First, we are asked to calculate the total number of sales

using the basic sum function.

So let's start by typing equal, followed by sum, and

then we're going to be summing the sales, which we know is called sales 2.

Notice how this total has changed.

It is now equal to 36,826.

Next we're going to calculate the total number of sales.

But this time we will be using the subtotal function to do so.

We start by typing equal followed by subtotal.

Now from the previous exercise we remember that sum was function number 9 in

the dropdown.

So we type 9 followed by a comma, and

then we know that we're summing the sales data, so we type sales 2.

You will notice that the basic sum formula is double counting

the total number of sales that are listed in the dataset.

It's counting both the individual records,

as well as the lines that have the subtotals in them.