this isn't about splitting a single dinner bill as the headline (Google Wants Patent On Splitting Restaurant Bills) suggests.
it's a little more complicated.. where, say, 5 people hang out together for a week, where multiple bills are paid individually by different people over the duration of the vacation or whatever and you need to "settle up" when you get home.
Yes, no matter how you slice it, it's just math (so whether or not you should be able to patent it is arguable) - but, if the patent is for the means by which it's tracked, and the design of the (i assume) app that you use to solve the equation, then a patent may have some merit.
You can solve this using Excel, but a dedicated app to to track the scenario mentioned in the original piece could be very useful to some.
"As an example, assume that a group is created to track and manage the expenditures of four friends (Friends 1-4) while on vacation in Miami. While on vacation, one of the days only three of the friends (Friends 1-3) go eat lunch at a restaurant because Friend 4 is not hungry at the time. The bill for lunch is $60 and Friend 1 pays the bill using a mobile payment service available on his device 104. Friend 1 adds the lunch as an expenditure of the group. When the form is presented to Friend 1 for the lunch, Friend 1 indicates that the lunch should be allocated to Friends 1-3. The lunch is not allocated to Friend 4 because Friend 4 did not participate in the lunch. Further, Friend 1 provides the following amounts of allocation in the form: Friend 1 $25, Friend 2 $16, and Friend 3 $19. In this example, the amount of allocation for each friend is based on what each friend ordered during lunch."
could be further "complicated" if your group of friends has vegetarians (where entrees are usually less than those with meat), and people who don't drink - so the cost of that bottle of wine should be split between the 4 of 6 in your party who actually had some. if someone brought their kids, that introduces yet another variable.
it'd be pretty cool to be able to take a picture of the itemized receipt and assign each line item to a person (drinks and entree), or the group (shared desserts, appetizers) - whatever is appropriate.
Banks are getting in to person to person transfers (using nothing but a mobile number or email address).. https://clearxchange.com/
the natural evolution of paying each other is to be able to request money FROM each other.. so i can use my credit card to pay for lunch, then send a note telling my friends they owe me $.
google couple potentially integrate with clearxchange, and card.io (take picture of CC instead of entering the number manually) to settle up once the costs are calculated.
this isn't a patent for a system to do math (addition, subtraction and division). this is a patent on a system that makes it so you don't have to think about the math.