In 7th or 8th grade kids are taught that a cone has 1/3 of the volume of the surrounding cylinder but not taught why. The model clearly shows this by breaking into three pieces of equal volume. The base circle is approximated by a regular polygon of many sides. As the number of sides increases
without limit, the ratio of volumes remains 1/3. No knowledge of calculus or limits is required to be convinced of the 1/3,2/3 result.