Addition, for example: 15+2= We tell children to keep the big number 15 in their hearts, and use their fingers to represent the small number 2 (let the children put their fingers out), with a "+"sign in the middle, that is, count their fingers from the number after 15, followed by1. ?

Subtraction, such as: 15-2= We tell our children: trust the big number 15, use your fingers to represent the small number 2 (let the children put their fingers out), and there is a "-"sign in the middle, which means counting backwards from the previous number 15, and the previous number 14.

Addition raises fingers in turn, subtraction clenches fingers in turn. When the number is more than ten and involves 6, 7, 8 and 9, the gestures are changed in turn, instead of raising or clenching the fingers.

Addition is one of the four basic operations, which refers to the calculation of combining two or more numbers and quantities into one number and quantity. The symbol of addition is the plus sign "+". Connect items with a plus sign when adding.

Subtraction is one of the four operations, and the operation of subtracting one number from another is called subtraction; Given the sum of two addends and one of them, the operation of finding the other addend is called subtraction. The symbol of subtraction is "-",which is pronounced as negative sign.