1. addition: remember large numbers in your mind and count up decimals, such as 4+2= remember 4 in your mind, count up 5 and 6, and then get the result of 4+2=6.

Second, subtraction: remember large numbers in your mind and count down decimals, such as 6-3= remember 6 in your mind and count down 5, 4 and 3, and then get the result 6-3=3.

Parents need to cooperate with their babies to do addition and subtraction within 30 words and 20 words every day to improve their arithmetic ability, and be careful not to let them count their fingers, develop habits that are difficult to change and cultivate their mental arithmetic ability.