Mathematical problem solving takes on many different forms and has long been established in school curricula with the terms, problems and problem solving taking on varied meanings. This article proposes a way of engaging students in mathematical open inquiry using a video clip as stimulus. It discusses findings from a recent study conducted in a Year 5 (9-10 years old) classroom in which the students' problem-posed and developed personal mathematical inquiries based on a video prompt. The article highlights the benefits for teachers and students in using video stimulus for open inquiry in Primary Mathematics classrooms.