The fast calculation method of multiplying two digits by 1 1 can be summarized as a formula: pull at both ends, add one in the middle, and make ten into one. Take 34× 1 1 as an example, 3+4=7, and then put 7 in the middle of 3 and 4, the result is 374; If we calculate 84× 1 1, 8+4= 12 according to the method of all decimals, the result is 924.

Elementary school 1 to grade 6 mathematics knowledge summary;

The first grade of primary school: 99 multiplication formula, learn basic addition and subtraction multiplication formula: recite 99 multiplication formula well and be familiar with single-digit multiplication formula;

The second grade of primary school: improve the multiplication formula table, strengthen the knowledge of the first grade, and learn the mixed operation of division and basic geometry;

The third grade of primary school: learn multiplication and commutation law, geometric area perimeter, time and unit. Distance calculation, distribution law, fractional decimal;

The fourth grade of primary school: the natural number of line angle is an integer, the prime factor is trapezoidal symmetry, and the fraction is calculated;

The fifth grade of primary school: multiplication and division of fractions and decimals, algebraic equations and average values, comparative size transformation, graphic area and volume;

Sixth grade: proportional percentage probability, circular fan, cylinder and cone.