The switch formula is the so-called single-even number switch formula, which means that a singular number can only be decomposed into the sum of a singular number and a double number, and a double number can be decomposed into two even numbers or the sum of two odd numbers.

For example, even number 6 can be decomposed into 1 and 5, and can also be decomposed into 2 and 4, where the former is two odd numbers and the latter is two even numbers. The singular number 5 can be decomposed into 1 and 4, and can also be decomposed into 2 and 3. Both the former and the latter are composed of a singular number and a double number.

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Kindergarten mathematics combination is a teaching method to cultivate children's mathematical thinking ability according to the mathematical thinking curriculum for 3-9 years old, with children as the center. Children in large classes have a certain foundation of mathematics knowledge and the ability to continue learning. But math knowledge is boring for children. Only when they have a strong interest in mathematics and a strong thirst for knowledge can they enjoy learning.

Mathematical combination is an exercise that children need to do before learning addition and subtraction. It is to decompose a natural number into several sums and make the sum equal to the original number. For example, 5 can be divided into 1 and 4, 2 and 3, 3 and 2, 4 and 1.

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