The scale is loaded with between 1 and 4 weights. The user then has to balance the scales, converting between g and kg in the process. There is a great deal of control over the level.
A great starter to explore addition, subtraction / difference and partitioning as well as the relationship between grams and kilog More…rams. Levels include converting whole kg to g (and vice versa), converting fractions of kg (eg 1/4kg = 250g) and weights in kg to 1 and 2 decimal places.