Six Divided by Two is Patented

I was reading through TechDirt when I came across this (Mike Masnick, TechDirt) article summarizing how IBM has filed a patent for determining how many passengers are in a vehicle. Naturally, I was a little skeptical that a company would try to patent something so trivial, so I thought the link might be to a less credible rumormill site. Instead, following the link took me to the actual patent filing, where I could see the details of the patent in all of its silliness. This is in stark contrast to the Apple patent filing (which I have written about before) which is downright creepy (but, in all fairness, rather clever and probably original). I figured that at least IBM would have a system that detects the motion and direction of passengers through the doors to determine who has entered and exited to then determine the weight of the bus.
Is it that complicated? Let me ask you this: should 6 divided by 2 be patented?
Why do I say that? The actual patent is nothing more than sifting through existing data showing seasonal average weights, weighing the bus when empty and filled, taking the difference and dividing by the appropriate average weight to arrive at a probable head count. Really?
This is nothing more than primary school subtraction and division. The only other things the patent calls for are a computer system and a GUI to assist in this calculation. There are a couple of sensors on the vehicle hooked up to the computer measuring the weights of various parts of the vehicle, so that these can be subtracted from the total weight reading.
I seriously hope that the courts don't let this one get through, but given their past actions, I think if someone mentions that mathematical operations (and this is one, rather than a complex piece of software) are not patentable, the judges are going to suffer collective amnesia.