Abacus Addition & subtraction 2,3 & 4 digits all combinations decimals 4 digits all combinations. Multiplication 3 & 4 digits x 1 digit, 2 digits x 2 digits. Division 2,3 and 4 digits ÷ 1 digits. Division 2 digits ÷1 digit Mental theory Addition & subtraction 2 & 3 digits all combinations decimals 3 digits all combinations Multiplication 2,3 and 4 digits x 1 digit