Based on our previous work on cognitive strategies for mental calculation, we present the design of a context sensitive computational system called ECOCAM, which aims to promote strategies for mental calculation in primary school students. We carry out a first test of our proposal through a specific implementation of the ECOCAM for an addition strategy task, that is to say the "transfer" strategy, in a pilot experiment and study case with boys and girls from different grades in basic education. We discussed the results and its implications for a future development and implementation of the ECOCAM.