Writing across the curriculum has been a pedagogy associated with faculty development since the earliest days of the movement. Carleton College, an early adopter of WAC pedagogy and faculty development, has, in the last decade, added portfolio assessment to the combination with positive results. Among the unexpected consequences has been a partnership with a curricular initiative in quantitative reasoning (QR), which has taken advantage of portfolio assessment as well as joint faculty development opportunities to successfully argue for the rhetorical power of numbers in teaching argumentation. We trace the history of WAC and QR at Carleton, describe the faculty development and assessment features, and argue that the combination of WAC and QR serves goals of liberal education: precision in language and ethical argumentation.