This brief report from the Indigenous Mathematics Project focuses on the way in which numerical reasoning is changing in the Oksapmin community of Papua New Guinea as a function of participation in new social institutions: economic exchange with currency and enrollment in school. Each of these new institutions means that arithmetic problems are framed in certain types of social interaction, in a culture which traditionally had no arithmetic problems. Their numeration system consists of enumerating 27 positions on the upper body with the 10 fingers, with some provision for counting further. How does one consider adding the nose to the shoulder? How they have adapted their indigenous system in order to communicate about currency is described in relation to problems at the tradestore. An examination revealed that adults with different levels of experience with a money economy solved problems in dramatically different ways. The school provides formal instruction on how to solve problems (in English). An arithmetic test showed that many children in grade 2 used the indigenous system, but only 10 percent used their bodies by grade 6. Interviews indicated the strategies they used. The report concludes that across both contexts the Oksapmin people are inventing new ways of using their traditional numeration system. (MNS)