While a substantial body of research suggests that adult numeracy and literacy learners possess funds of knowledge and informal practices, it is not always clear to what extent these might be used in teaching and learning. In this study of linguistic interaction in adult numeracy classrooms, analysis of naturally-occurring student-student collaborative discourse is used to argue that mathematical word problems, even when designed for adults, do not draw on these funds of knowledge and out-of-classroom practices, and instead require a "willing suspension of disbelief" by learners. Nonetheless, the adult students show a sophisticated level of metacognition and skill in handling the word-problem genre which might indeed be acknowledged as part of their funds of knowledge.