The mixed operations of addition and subtraction within 20 are generally 1 bit plus 1 bit,1bit plus1bit,1bit plus1bit, and the same is true for subtraction. The mixed operation follows the mixed operation of general numbers, multiplying first, then dividing, and then adding and subtracting. If there are brackets, the brackets are counted first, and the brackets are counted outside.

For example: 1.6+0.8=2.4

(3. 1+0.5)-0. 1=2.5

1.6-0.5+0. 1= 1.2

Hybrid algorithm

(1) If there is only addition and subtraction in the formula, it will be calculated in turn; Only multiplication and division are calculated in turn.

(2) There are both addition and subtraction and multiplication in the formula. Multiplication first, then addition and subtraction.

(3) There are both addition and subtraction and division in the formula. Calculate division first, then add and subtract.

(4) The parts that are not involved in calculation in each step should be copied down with the same position and symbols to ensure that the equal sign is equal before and after.

(5) The function of parentheses in mixed operation is to change the operation order. Operation sequence of mixed operation with brackets: first calculate the inside of brackets, then calculate the outside of brackets.