Rounding, see if you want to keep integer or several decimal places, and then directly round to less than 4 according to the last digit, and add 1 to the previous digit greater than or equal to 5. For example: keep an integer, 2.4 ≈ 2; 2.5≈3。 Keep one decimal place, 2.24 ≈ 2.2; 2.25≈2.3