58-37 = (50 + 8 ) - ( 30 + 7) = ( 50 - 30 ) + ( 8 - 7) = 20 + 1 = 21
72-51 = ( 70 + 2) - ( 50 + 1) = ( 70 - 50) + ( 2 - 1) = 20 + 1 = 21
71-51 = ( 70 + 1) - ( 50 + 1) = ( 70 - 50) + ( 1 - 1) = 20 + 0 = 20
783-541 = ( 700 + 80 + 3) - ( 500 + 40 + 1) = (700 - 500) + (80 - 40) + (3 - 1) =
= 200 + 40 + 2 = 242
837-615 = ( 800 + 30 + 7) - (600 + 10 + 5 ) = ( 800 - 600) + (30 - 10) + ( 7 - 5) =
= 200 + 20 + 2 = 222
855-54 = ( 800 + 50 + 5) - ( 50 + 4) = 800 + ( 50 - 50) + (5 - 4) =
= 800 + 0 + 1 = 801
342-22 = ( 300 + 40 + 2) - ( 20 + 2) = 300 + ( 40 - 20) + ( 2 - 2) =
= 300 + 20 + 0 = 320
2)
346 - 21 = 325 ( уч.) - во второй школе
346 + 325 = 671 ( уч.) - всего
ответ: 671 ученик.
2000 122402 54415 5997698 l 122402 65700
- 1951 * 49 +67987 -489608 l 49 - 49
49 1101618 122402 1101618 65651
+ 489608 - 1101618
5997698 0
б) (127563+52437) : 30 + 870000 : 100 + 7984 = 196684
127563 180000 l_30 870000 l 100 180000 188700
+ 52437 18 l 600 800 l 8700 + 87000 + 7984
180000 0 700 188700 196684
в) (3551 : 53 + 3599 : 59) * 400 - 15911 = 35289
3551 l 53 3599 l 59 67 128 51200
- 318 l 67 - 354 l +61 * 400 -15911
371 59 128 51200 35289
-371 - 59
0 0