Students have fixed capital and must create ëwidgetsí (folded and stapled paper); labor is increased in each round. Resulting production data is used to calculate total, marginal and average production and costs. [decreasing marginal product/increasing marginal costs]
For large classes, can be done with a sub-set of students as a demonstrations for the rest of the class.
There are many ways to vary this activity by varying the good produced (e.g., this variation is about making peanut-butter and jelly sandwiches).