Вычислите: 1) 3/7+4/9; 2) 8/9-7/8; 3) 13/15-2/3; 4) 20/21+3/7; 5) 17/18-11/12; 6) 7/16+1/6; 7) 2/9+5/6; 8) 10/21+9/14; 9) 7/9-4/15; 10) 9/14-3/7+15/28 11) 1/6+1/4-1/8 12) 13/18-29/45+8/15

Question

Otika

Математика

5 июля, 00:19

Вычислите: 1) 3/7+4/9; 2) 8/9-7/8; 3) 13/15-2/3; 4) 20/21+3/7; 5) 17/18-11/12; 6) 7/16+1/6; 7) 2/9+5/6; 8) 10/21+9/14; 9) 7/9-4/15; 10) 9/14-3/7+15/28 11) 1/6+1/4-1/8 12) 13/18-29/45+8/15

+5

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Александр Смирнов · Answer 1

Найдем значение выражений:

1) 3/7 + 4/9 = 27/63 + 28/63 = (27 + 28) / 63 = 55/63;

2) 8/9 - 7/8 = 64/72 - 63/72 = (64 - 63) / 72 = 1/72;

3) 13/15 - 2/3 = 13/15 - 10/15 = (13 - 10) / 15 = 3/15 = 1/5;

4) 20/21 + 3/7 = 20/21 + 9/21 = (20 + 9) / 21 = 29/21 = 1 8/21;

5) 17/18 - 11/12 = 34/36 - 33/36 = (34 - 33) / 36 = 1/36;

6) 7/16 + 1/6 = 21/48 + 8/48 = (21 + 8) / 48 = 29/48;

7) 2/9 + 5/6 = 4/18 + 15/18 = (4 + 15) / 18 = 19/18 = 1 1/18;

8) 10/21 + 9/14 = 20/42 + 27/42 = (10 + 20) / 42 = 30/42 = 5/7;

9) 7/9 - 4/15 = 35/45 - 12/45 = (35 - 12) / 45 = 23/45;

10) 9/14 - 3/7 + 15/28 = 18/28 - 12/28 + 15/28 = (18 - 12 + 15) / 28 = 21/28;

11) 1/6 + 1/4 - 1/8 = 4/24 + 6/24 - 3/24 = (4 + 6 - 3) / 24 = 7/24;

12) 13/18 - 29/45 + 8/15 = 65/90 - 58/90 + 48/90 = (65 - 58 + 48) / 90 = 55/90 = 11/18;