What is the formula of mental arithmetic?

What is the formula of mental arithmetic?

① Abacus formula (abacus addition formula table): the non carry plus carry plus straight top five plus ten plus break five into ten plus one up one down five go four one go nine into one two up two down five go three two go eight into one three up three down five go two three go seven go one four up four four down five go one four go six into one five five up five five five go five into one six Six up, six down, four in, six up, one down, five in, seventeen up, seven out, three in, seventeen up, two out, eighteen up, eight out, two in, eighteen up, three out, five in, nine out, one in, nineteen up, four out, five in, one abacus addition formula table Abdication decrease ten make up five decrease one by one next one up four go five one back one return nine two down two two up three go five two back one return eight three down three up two go five three back one return seven four down four up one go five four back one return six five five five back one return five six six back one return four six back one return five go one seven back seven seven back one return three (3) abacus multiplication formula table: abacus multiplication formula table: abacus multiplication formula table is exactly the same as the table multiplication formula used in oral and written calculation, that is, big 99 formula table. 1 & times; 9 = 9 2 & times; 9 = 18 3 & times; 9 = 27 4 & times; 9 = 36 5 & times; 9 = 45 6 & times; 9 = 54 7 & times; 9 = 63 8 & times; 9 = 72 9 & times; 9 = 81 for more detailed multiplication formula table of abacus, please click to view it, download address of multiplication formula table of abacus: ④ abacus formula table (division formula table: there are two kinds of division methods of abacus and quotient Division) division method is calculated with formula, there are nine return formula, There are 61 sentences in the formula: one return (divide by 1): every one into one, every two into two, every three into three, every four into four, every five into five, every six into six, every seven into seven, every eight into eight, every nine into nine. Two return (divide by 2): every two into one, every four into two, every six into three, every eight into four, every two into five. Three return (divide by 3): every three into one, every six into two, every nine into three, Four GUIs (divide by 4): every four into one, every eight into two, four into two, four into five, four into two, four into seven into two. Five GUIs (divide by 5): every five into one, five times into two, five times into four, five three times into six, five times into eight. Six GUIs (divide by 6): every six into one, every twelve into two, six three into five, six under six plus four, six two, six four four, Seven GUIs (divided by 7): every seven into one, every fourteen into two, seven one plus three, seven two plus six, seven three four plus two, seven four five plus five, seven five seven plus one, seven six eight plus four. Eight GUIs (divided by 8): every eight into one, eight four plus five, eight one plus two, eight two plus four, eight three plus six, eight five six plus two, eight six seven plus four, eight seven plus four, eight seven plus six. Nine GUIs (divided by 9): every nine into one, Nine one plus one, nine two plus two, nine three plus three, nine four plus four, nine five plus five, nine six plus six, nine seven plus seven, nine eight plus eight, There are nine pithy formulas: see one nothing except for ninety-one, see two nothing except for ninety-two, see three nothing except for ninety-three, see four nothing except for ninety-four, see five nothing except for ninety-five, see six nothing except for ninety-six, see seven nothing except for ninety-seven, see eight nothing except for ninety-eight, see nine nothing except for ninety-nine