All of Quadrivium's Comments + Replies

Don't leave us hanging... Could you please provide one or two more examples?

 

34-16=12?

63-17=11?

2Valentine6mo
34–16 yields 13 63–17 yields 16
4Duncan_Sabien6mo
The point was usually to illustrate a variety of different mental motions that a young mathematician might be making, OTHER than the one intended by the algorithm. So all sorts of examples are possible, and there were a number of things found in clinical interviews. Not just instances of one single pattern.