This little prompt caused some serious debate in my S3 class. The pupils had only just learned about compounding and were still working things out repeatedly. The motivation of this task was to set up a rationale for using x 1.03^20 instead of laboriously doing 20 different calculations.

The context added some emotional energy to the lesson, while the consideration of the weight is an addition I only considered once they had left the room, but will be sure to add tomorrow.

Credit: @chrismcgrane84