PS

NOTE: You can download the individual movies from here.
The foregoing task involves fairly basic geometric knowledge (about area of triangle in particular), but also needs insight. This makes it educationally very appealing and Melissa Rodd and I have used it a lot on the Geometry MA module at IoE. I don't remember where we got it from, though it features, for example, in Developing Thinking in Geometry (edited by Sue Johnston-Wilder and John Mason).

The task is closely related to Vecten's configuration, shown above (though the above task is much more challenging I think). Vecten was a 19th century French mathematician who worked in Nîmes.

If you have any methods or comments about the original task, please email MT, post a comment on the MT/ATM website or send an email to info@mathsmed.co.uk PPS: You can find another variant here.