Simple calculation is a special calculation method, which makes the calculation simple and a very complicated formula easy to calculate by using the algorithm and the basic properties of numbers.

There are three main methods: addition and subtraction rounding, grouping rounding and raising common factor.

They all use the idea of splitting and rounding in mathematical calculation.

Main steps:

① When encountering a complex formula, first observe whether it is possible to round up;

(2) Make a whole 100 by four operations, and then make a simple calculation.

Addition-subtraction rounding method

1, split a certain number in the calculation formula, so that it can make a whole ten and a whole hundred with other numbers;

2. Add a number, which can be rounded by other numbers, and then subtract this number.

Group rounding method

In the calculation problem with only addition and subtraction, the items in the calculation formula are recombined and rounded, and two formulas are mainly adopted: Teacher G talks about the Olympic number (micro).

Additive associative law: a+b+c = a+(b+c) = (a+b)+c;

The essence of subtraction: a-b-c=a-(b+c).

Methods of improving common factor

Find the common factor by multiplication and division, a x (b c) = a x b a x c;

If there is no common factor, the common factor can be changed according to the multiplicative associative law.

a×b=(a× 10)×(b÷ 10)，

a×b \c = a \c×b，

a×b×c=a×(b×c).