Decimal number method: several numbers are added together. If the single digits of two addends add up to 10, the two numbers can be added first, and the ten digits within 10 can be added to 1.

Addition and subtraction in the unit of close to 10 (in the unit of 9): You can calculate this addend (or subtraction) as 10 first, and then add 1 (or subtract 1) to get the final result.

Oral calculation method: first add up the whole ten, then add up the digits, and finally add up the sum obtained by adding these two. Written calculation method: first add the first two numbers, and then add the third number to sum up. Or directly add three numbers vertically, align the same numbers, start with one number, and add ten numbers to each number to advance several numbers.

As follows:

Mathematics (Mathematics or maths, from the Greek word "Má thē ma"; Often abbreviated as "mathematics"), it is a discipline that studies concepts such as quantity, structure, change, space and information, and belongs to a formal science from a certain point of view. Mathematicians and philosophers have a series of views on the exact scope and definition of mathematics.

In the development of human history and social life, mathematics also plays an irreplaceable role, and it is also an indispensable basic tool for studying and studying modern science and technology.

Aristotle defined mathematics as "quantitative mathematics", which lasted until18th century. /kloc-since the 0/9th century, mathematical research has become more and more rigorous, and it has begun to involve abstract topics such as group theory and projection geometry that have no clear relationship with quantity and measurement. Mathematicians and philosophers have begun to put forward various new definitions.

Some of these definitions emphasize the deductive nature of a lot of mathematics, some emphasize its abstraction, and some emphasize some themes in mathematics. Even among professionals, the definition of mathematics has not been reached. Whether mathematics is an art or a science has not even been decided.