In a twist on Craig Barton’s SSDD problems, I sometimes find that Different Surface, Same Depth (DSSD) problems can be useful. I find this sort of task more impactful some time after pupils have first encountered the idea. If we were working quadratic inequalities then I issued this, there might be an assumption that’s what would be involved here too. Instead, some weeks later I will issue this task. Pupils first of all have to discern that a quadratic inequality has arisen and then be able to solve it. Many pupils, in my experience, fail to identify quadratic inequalities when they arise in other contexts. Of course, when I issue this task I will not tell pupils that quadratic inequalities are present. Instead, I’ll let them stumble upon it.