This, for me, is an example of Task Design of the highest level. Segar Rogers is quite the master at it. It takes something which can often be taught procedurally and opens it up into something much more. It’s a problem solving, sense making, bar model utilising task. Careful variation of the given variables help pupils to get a proper sense of this idea. In real life I have never once written down an SDT triangle. Instead, I’d use proportional reasoning. This is exactly what Segar gets at here. A lovely touch is how some of the icons of the mode of transport are missing and pupils need to decide what would be a sensible suggestion for the given distance, speed and time in those rows.