At present, there is no special requirement for you to approximate the approximate number in the second year of high school, and there is no same standard. The following requirements can be made: if it is four digits, it will be approximated to one hundred digits; If it is three digits, it is close to ten digits. Keep the same number of digits on the same topic. That is to say, if ten people are reserved, everyone will keep ten people; If you make an appointment to 100, make an appointment to 100 at the same time.

For example: ①4 16-25 1≈70 (both numbers are reserved to the decimal digits), ② 416-251≈/00 (both numbers are reserved to the hundredth digits), ③ 4/kloc. ④ 416-25 1 ≈ 50 (416 is reserved to the hundredth place, about 400, and 251reserved to the tenth place, about 250).