20 примеров на вычитание дробей с разными знаминателями

1) 3/5 – ¼ = 3 * 4/20 – 1 * 5/20 = 12/20 – 5/20 = 7/20;

2) 5/8 – 3/7 = 5 * 7/56 – 3 *8 /56 = 35/56 – 24/56 = 11/56;

3) 13/15 – 4/5 = 13/15 – 4 *3/15 = 13/15 – 12/15 = 1/15;

4) 1/5 – 2/9 = 1 * 9/45 – 2 *5/45 = 9/45 – 10/45 = - 1/45;

5) 4/7 – 5/11 = 4* 11/77 – 5 *7/77 = 44/77 – 35/77 = 9/77;

6) 2/9 – ¾ = 2 * 4/36 – 3* 9/36 = 8/36 – 27/36 = -19/36;

7) ¾ - 12/19 = 3 * 19/76 – 12 * 4/76 = 57/76 – 48/76 = 9/76;

8) 1/6 – 9/19 = 1 * 19/114 – 9 * 6/114  = 19/114 – 54/114 = -35/114;

9) 2/3 – 7/8 = 2 * 8/24 – 7 * 3/24 = 16/24 – 21/24 = -5/24;

10) 7/24 – 1/12 = 7/24 – 1 * 2/24 = 7/24 – 2/24 = 5/24;

11) 9/14 – 1/7  = 9/14 – 2 * 1/14 = 7/14 = ½;

12) 2/3 - 6/17 = 2 * 17/51 – 6 * 3/51 = 34/51 – 18/51 = 16/51;

13) 3/8 – 11/16 = 3 * 2/16 – 11/16 = 6/16 – 11/16 = -5/16;

14) 2/13 – 6/7 = 2 *7/91 – 6 * 13/91 = 14/91 – 78/91 = -64/91;

15) 5/21 – 3/5 = 5 * 5/105 – 3 * 21/105 = 25/105 – 63/105 = -38/105;

16) 8/9 – 11/12 = 8 * 4/36 – 11 *3/36 = 32/36 – 33/36 = -1/36;

17) 7/11 – 4/15 = 7 *15/165 – 4 * 11/165 = 105/165 – 44/165 = 61/165;

18) 3/16 – 5/6 = 3 * 6/96 – 5 *16/96 = 18/96 – 90/96 = -62/96 = -31/48;

19) 4/31 – 2/3 = 4 * 3/93 – 2 *31/93 = 12/93 – 62/93 = -50/93;

20) 3/7 – 5/23 = 3 * 23/161 – 5 * 7/161 = 69/161 - 35/161 = 34/161.