Yeah I get the part about filling in some missing foundation. But it's the level that surprised me. Some of the MU123 content is covered in 5th grade in the US,

Yeah I get the part about filling in some missing foundation. But it's the level that surprised me. Some of the MU123 content is covered in 5th grade in the US, i.e. around age 10 or 11. But I guess there are people who will have forgotten that stuff, if they're not using much math day to day.