Вычислите: 1) 1/4 + 3/5; 4) 3/28 + 5/14; 7) 9/25 - 7/20; 10) 9/16 + 7/24 - 3/8 2) 9/11 - 2/5; 5) 14/15 - 7/10; 8) 37/42 - 17/24; 11) 1/3 - 1/6 + 1/4; 3) 13/16 - 9/32; 6) 3/8 + 1/6; 9) 11/24 - 13/16; 12) 2/5 + 4/15 - 5/9.

Question

Андрей Климов

Математика

10 апреля, 11:36

Вычислите: 1) 1/4 + 3/5; 4) 3/28 + 5/14; 7) 9/25 - 7/20; 10) 9/16 + 7/24 - 3/8 2) 9/11 - 2/5; 5) 14/15 - 7/10; 8) 37/42 - 17/24; 11) 1/3 - 1/6 + 1/4; 3) 13/16 - 9/32; 6) 3/8 + 1/6; 9) 11/24 - 13/16; 12) 2/5 + 4/15 - 5/9.

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Виктор Воронин · Answer 1

1) 1/4 + 3/5 = (1*5 + 3*4) / 20 = (5+12) / 20=17/20;

2) 9/11 - 2/5 = (9*5-2*11) / 55 = (45-22) / 55 = 23/55;

3) 13/16 - 9/32 = (13*2 - 9*1) / 32 = (26-9) / 32 = 17/32;

4) 3/28 + 5/14 = (3*1+5*2) / 28 = (3+10) / 28 = 13/28;

5) 14/15 - 7/10 = (14*2 - 7*3) / 30 = (28-21) / 30 = 7/30;

6) 3/8 + 1/6 = (3*3 + 1*4) / 24 = (9+4) / 24 = 13/24;

7) 9/25 - 7/20 = (9*4-7*5) / 100 = (36-35) / 100 = 1/100;

8) 37/42 - 17/24 = (37*4-17*7) / 168 = (148-119) / 168 = 29/168;

9) 11/24 - 13/16 = (11*2-3*3) / 48 = (22-9) / 48 = 13/48;;

10) 9/16 + 7/24 - 3/8 = (9*3+7*2-3*6) / 48 = (27+14-18) / 48 = 23/48;

11) 1/3 - 1/6 + 1/4 = (1*4-1*2+1*3) / 12 = (4-2+3) / 12 = 5/12;

12) 2/5 + 4/15 - 5/9 = (2*9+4*3-5*5) / 45 = (18+12-25) / 45 = 5/45 = 1/9.