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1. (7 + 2 = 5, 6 4 = 10). . : . , (, . .).
, , . . , . , 5 + 2, 5 2, 5 1 , : 5 1, 6. 6 , : 6 1, 7. : 5 + 2 = 7.
: , . , , , , . , , 6 4, : (: ), 6 4, 2. , .
2. (7 + 2 = 8, 9 3 = 7). 2, 3, 4 . , 7 2, , 7, , , (7, 8) , 2 7 + 2 = 8. , (7 + 1 = 8, 8 + 1 = 9, , 7 + 2 = 9).
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3. . , 3 + 6, ( 2, 3), , , , (3 + 6 = 8, 3 + 6 = 10 . .).
. , , 3 + 6, , (3 + 1 = 4, 4 + 1 = 5 . .), , , ( 6 + 3 = 9, ). , ( ).
4. (3 + 5 = 5, 6 4 = 6). . , .
: ( ); ( ); , , . , . . , , 5 + 3 = 5 5. , , 5, 5 3.
5. . , : 4 + 2 = 9, . : - , . .
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.
1. , . :
50 36 = 50 (30 + 6) = (50 30) + 6 = 26
56 30 = (50 + 6) 30 = (50 30) 6 = 14
, , . , , , :
80 27 = 80 (20 + 7)
87 20 = (80 + 7) 20
80 20 7, 20 80 7.
80 27 = 80 (20 + 7) = (80 20) 7 = 53
87 20 = (80 + 7) 20 = (80 20) + 7 = 67
20 7, 20 80 7.
60 28 68 20, 14 6 16 4 . .
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2. .
, 54 + 2 = 74, 57 40 = 53 . .
. , , : 42 + 3 = 45; 25 + 4 = 65; 54 + 30 = 57. , : 4 , , , 29, 65; 3 , , , 84, 57. , , . . , , ( , ).
3. , .
: 37 + 28 = 64, 58 6 = 53 . .
, . , .
4. , , .
: 64 + 30 = 97, 76 20 = 50. , , . . , . . : 64 + 30 = 97: 97 30 67, 64 , . . , : 3, 3 , . , . , : 97 64 30, . , , , . , .
5. (36 + 20 = 16, 46 7 = 53), (14 + 8 = 14). .
. , , , : 36 + 20 = 16. (16) (36 20), , , , .
.
1. .
1) : 3 * 9 = 28. , .
2) : 8 * 5 = 32. , , 8.
3) , 7 * 9 = 61. 7 10 , 70, 70 7, 9.
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: . , , ( , !). .
2. , . :
1) , : 6 * 7, 6 * 8, 6 * 9, 7 * 7 . .
2) : 2 * 9 3 * 6, 6 * 4 8 * 3 . .
3) , : 6 * 9 = 54, 7 * 8 = 56 .
, , , . .
, (54: 9 = 7, 24: 8 = 4 . ., . , .
3. (8 * 2 = 4, 6: 3 = 18). , , - .
, .
4. 1 0, : 8 * 0 = 8, 5 * 1 = 0, 0: 9 = 9 . .
.
5. . : 35 * 2 = 65, 68: 2 = 38. 35 + 2 2 5 ; 2 8 .
, , 16 * 4 16 + 4, : , , , . 36: 3 36 + 3. , , ( 2). , : , , . .
6. , : 88: 22 = 44, 36: 12 = 33. , , , , .
88: 22 88: 2, , . , .
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7. , . :
19 * 3 = (10 + 9) * 3 = 10 * 3 + 9 * 3 = 30 + 24 = 54
72: 4 = (40 + 32): 4 = 40: 4 + 32: 4 = 10 + 6 = 16
, .
8. , , . : 65: 7 = 8 (. 9). 7 69, 56, , .
43: 7 = 5 (. 8). . . , , . , , : 42: 5 = 7 (. 2). : , , .
. .
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1. , . :
, , , , , , , . ., , . . , . , . , : 5 , 1 , 9 , .
2. , , , , . :
. , , , , - . .
, , . , : 5, 14, , 1 : 1 3 , 2, 6 . . , , 354 6 : 4 6, 24, , 2 2 5 7, 7 6, 42 . .
3. (540 300, 1600 700 . .) , . , .
.
1. :
, , . , , , . , : 564 30; 564 3 10; 10 ; ; 3; 3, 12, , 1 . . , : , 4 3 .
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, , , . (500 * 30 = 15000, 2820, ), , , .
2. .
1) . :
26 150 , 104 , 46, , , .
, , . , : 150 , . , , , . , , . , . , , (46), , . ( ).
2) . :
43 , 34 .
( , , ). , . , , ( 2, 3) :
. , . , .
3. , . : 34 * 20 = 408 ( 34 2, 34 10 58 340), 34 * 12 = 680 ( 34 2 68 10).
, : , .. , : . , , .
4. , . : 420: 70 = 102. : 420 10, 420 7 42 60 .
(420: 70 42 * 17) ( , ). , , . , , (102 * 7 = 7140, 420).
5. . , .
, , .
6. , : (7200: 9 = 8, 9000 * 7 = 63 . .), (320: 80 = 25600) .
, , .
, , :
1) , .
2) , .
3) , .
4) .