In mathematics, ≈ means approximately equal. For example, 8.65 equals 8.7, which can be done according to the principle of rounding. When calculating this kind of questions, if you add or subtract, it is more convenient to treat the two numbers as integer hundred, integer thousand or integer ten, and then add or subtract the approximate numbers to get the final answer. In the case of multiplication and division, the number with more digits is regarded as an integer hundred, an integer thousand or an integer ten, and then the final answer is obtained by multiplication and division. For example, pi is 3. 14 15926, but it is usually 3. 14 when calculating.

This kind of topic mainly examines students' estimation or quick calculation methods, helps students improve their sense of numbers, and exercises this kind of topic can improve students' ability to apply mathematics in life. The situation of addition, subtraction and further subtraction appeared after the rounding method was systematically studied. By this time, students should have learned decimal places. The title will be accurate to the whole number or keep 2 decimal places. This is the rounding method that we contact and use most often.