, .
:
() , :
430 + 210 = 430 + (200 + 10) = (430 + 200) + 10 = 640
540 430 = 540 (400 + 30) = (540 400) 30 = 110
:
430 + 210 = (400 + 30) + (200 + 10) = (400 + 200) + (30 + 10) = 640
540 430 = (500 + 40) (400 + 30) = (500 400) + (40 30) = 110
, 1, .
IV. .
1. 1000 :
, 397 402, 756 763;
, 1, 0, 8 ( ), ;
;
, 1, 200 (499, 701, 999);
, 1, 300 (501, 1000, 899).
2. . 2 :
3 24 .
? . .
2 28 .
4 . , 2 , . , 3 , . , , .
1