So how does the "breaking ten method" "break ten" in concrete calculation?
For example:? 15-8,
When calculating 15 minus 8, considering that the single digit 5 minus 8 is not enough, we divide 15 into 10 and 5, subtract 8 from 15 to get 2, and then add 2 to the remaining 5 digits to get 7.
The breakdown is as follows:
The formula of breaking the law of ten: look at a large number, divide it by 10, then subtract it, and add the remainder.
Ten MINUS nine, a few plus one. Ten MINUS seven, a few plus three. Ten MINUS five, a few plus five. A dozen MINUS three, a few plus seven. Ten MINUS eight, a few plus two. Ten MINUS six, a few plus four. Ten MINUS four, a few plus six. A dozen MINUS two, a few plus eight.
"Breaking the Ten Laws" means opposing the Ten Laws. Just let the children know that a dozen can be divided into 10 and a few, and a few+a few equals a few.
I want to add and subtract.
It is to use the relationship between addition and subtraction to get the result of subtraction from addition. The basic idea of learning abdication subtraction within 20 is to think about the corresponding addition within 20, which is basically to calculate subtraction by using the inverse operation relationship of addition and subtraction.
As required, 15-8= (? ), you have to think about 8+ (? ) = 15, because 8+(7)= 15, 15-8=7. The whole thinking process not only uses 8+7= 15, but also uses the knowledge that 8 and which number add up to 15.
Second, the flat ten method
The key of the equal ten method is to analyze that the unit is not reduced enough, and then decompose the subtraction into two numbers.
In other words, two numbers in the same position (commonly known as mantissa) can be subtracted, just cut off the tail. For example, subtracting 5 from 15 means cutting off the tail of 5, leaving 10. Then subtract a number from an integer ten, and it is very easy to calculate.
For example: or 15-8=? For example, it can be calculated by continuous subtraction, and 15 is subtracted by 5 and then by 3. That is15-8 =15-5-3 =10-3 = 7.