Adding numerators and denominators to find the "mediant" is sometimes called "doing a freshman sum". In some countries I gather this is introduced as a separat

Adding numerators and denominators to find the "mediant" is sometimes called "doing a freshman sum". In some countries I gather this is introduced as a separate operation (see page 23 in the translation of a Soviet primary school textbook by Gelfand linked below). https://en.wikipedia.org/wiki/Mediant_(mathematics) https://en.wikipedia.org/wiki/Mediant_(mathematics) https://www.cimat.mx/ciencia_para_jovenes/bachillerato/libros/algebra_gelfand.pdf https://www.cimat.mx/ciencia_para_jovenes/bachillerato/libro...