Maths Teaching Idea #3

Do we need actual measurements to work on shape problems?

I was inspired by a Median Don Steward question on cones and spheres here. This question wasn’t meant to be especially challenging but was meant to push learners into thinking about starting a shape question that seemingly has no given lengths.

The first step of taking the base of the triangle to be 2r should be justified by students: “what part of the question allows you to make this assumption?”.