In this chapter, we challenge the view of mathematical modelling as a neutral practice and argue that ethical reasoning is an important part of the process. Using six cases, each describing different sharing scenarios, we analysed children’s mathematical reasoning and ethical reasoning. The cases were designed to cover a variety of aspects of mathematics and allow different types of ethics to be used. The results show that ethical reasoning plays a crucial part in task-solving, both when the children advocated for division or when they decided on sharing in unequal-sized parts.