SUM filtered rows in LibreOffice using SUBTOTAL

In Libre Office Calc you sometimes need to filter data using the Autofilter. And of course you would like to know the sum of the values filtered. This is where you'll want to use the SUBTOTAL() function. To get the subtotal of the filtered values you'll need to tell the subtotal function which function you would like to use on the filtered rows.

LibreOffice 4.1 Solver example

While going through my accounting I found some discrepancies. So I needed to go through a long list of numbers and check whether they have been included in the totals I was checking.
Of course I would like not having to spend hours doing this, so I decided to find out how I could do this using LibreOffice Calc an save myself a lot of time. The time spent making the calculation is now about 1 second. (The time spent figuring this out... Let's just say hours....)