Take "minus nine plus one" as an example. "Minus nine plus one" refers to a number MINUS nine, and the result of adding 1 to the unit of this number is their difference.
Subtraction of abdication means that when two numbers are subtracted and the number of digits to be subtracted is not enough, borrowing the previous digit is equivalent to adding 10 to this digit and then calculating.
Subtraction follows several important patterns. It is anti-commutative, which means that changing the order will change the sign of the answer. It is not associative law, that is, when a subtraction exceeds two numbers, the order of subtraction is very important. Subtracting 0 does not change a number.
The formula of learning mathematics in the first grade of primary school
1, add up to ten methods.
Good friends1919,2828, hand in hand, 3737 is really close, and 4646 will go together. Make a pair of hands in half.
One plus nine, ten tadpoles, two plus eight, ten old ducks, three plus seven, ten old hens, four plus six, ten golden monkeys, five plus five, and ten big tigers.
Think of 1 when you see 9, 2 when you see 8, 3 when you see 7, and 4 when you see 6.
When you see the big corner decimal system, switch the two numbers first.
Carry addition within 2.20
(1) Children should remember "9 to 1", "8 to 2", "7 to 3", "6 to 4" and "5 to 5".
(2) The method of ten plus one is simple, and the thinking process includes "one look (at large numbers), dichotomy (at decimals), three plus ten, and four plus".
(3) Look at large numbers, divide them into decimals, add them to ten, and add the remainder.