Addition and subtraction formula within 20

Addition and subtraction formula within 20: look at large numbers and divide them into decimals. Made ten, plus the rest. Clap your hands, children. Let's sing ten songs. One equals nine, two equals eight, three equals seven, four equals six and five equals ten.

Addition and subtraction technique

1, addition: remember a large number in your mind, count the decimal up, for example, 4+2= remember 4 in your mind, count up two numbers, 5 and 6, and then get the result 4+2=6.

2. subtraction: remember large numbers in your mind and count down decimals, such as 6-3= remember 6 in your mind and count down 3, 5, 4, 3, Then the result is 6-3=3.

Carry addition formula: "add nine MINUS one, add eight MINUS two, add seven MINUS three, add six MINUS four, add five MINUS five." How to use the formula? Take "plus nine MINUS one" as an example. "Add nine and subtract one" refers to the addition of a number and 9, and the number minus 1 is the unit of their sum.

Tips for addition and subtraction in 20 minutes:

No carry addition and subtraction within 20

1, 1 1-20 numbers can be used to play guessing games with children.

2, the unit is 2, and the decimal number is 1.

3, 1 10, 5 one.

4. More than 1 1 and less than 13.

Describe the numbers in these ways and let the children guess, or vice versa, until they are proficient.

Dial the number with the counter. Parents say the number and children dial the number. A composition that is said while dialing. For example, 12 consists of 1 tens and 2 ones.

In the mathematics teaching of senior one, carry addition and abdication subtraction within 20 are both the focus and the difficulty of teaching. General children learn the addition and subtraction within 10 in preschool. After entering primary school, they can master the addition and subtraction within 20 with a little practice, without carrying or abdicating.