It means that two numbers close to an integer are calculated as integers first, and then the part that becomes an integer is calculated additionally after the calculation is completed, so it is written as 702-197 = 700+2-200+1= 500+5 = 505.

This is the learning range of second grade mathematics. The second grade mathematics needs to know the counting units "hundred" and "thousand", know the decimal relationship between two adjacent counting units, master the digit order within ten thousand, read and write the digits within ten thousand, know the composition of the digits within ten thousand, compare the sizes of the digits within ten thousand, describe the sizes of the digits within ten thousand with symbols and words, and understand and recognize the approximate figures within ten thousand.