Grade school math fellas. Aint rocket science. I have seen college students stumped by 2+3×4=. How many Japanese third graders you think are stumped by it?
As to Japanese grammar school kids and their math skills, all I have is, the last thing they think about is math when a group of ugly American kids jumps your ass, roughs ya up a bit and smashes your abacus into pieces. Take that, son of Tojo... Man I hope my grandpa wasn't looking down from the clouds back then. "Hey Pop I had a horrible nightmare last night and your dad I never met was in it yelling at me and he seemed really upset. BTW, does the word 'seppuku' mean anything to you? Just curious...."