Сравните дроби:а)19/20 и 7/8б)11/12 и 9/10в)0,4 и 3/7Выполните деяния:а)6 5/12 +

1. а) 19/20 gt; 7/8, т.к. 38/40 gt; 35/40;  б) 11/12 gt; 9/10, т.к. 55/60 gt; 54/60;  в) 0,4 lt; 3/7, т.к. 4/10 lt; 3/7 =  28/70 lt; 30/70.

2. а) 6 5/12 + 3 3/8 = (6+3) + (5/12+3/8) = 9 + (10/24+9/24) = 9 19/24;

б) 2 11/20 + 4 19/30 = (2+4) + (11/20+19/30) = 6 + (33/60+38/60) = 6 71/60 = 7 11/60;

в) 3 - 18/19 = 2 19/19 - 18/19 = 2 + (19/19-18/19) = 2 1/19;

г) 5 6/7 - 3 1/14 = (5-3) + (6/7-1/14) = 2 + (12/14 - 1/14) = 2 11/14;

д) 2 3/10 - 1 7/15 = (2-1) + (3/10 - 7/15) = 1 + (9/30 - 14/30) = 30/30+9/30-14/30 =39/30 - 14/30 = 25/30 = 5/6;

е) 10 - 2 2/9 = 9 9/9 - 2 2/9 = (9-2) + (9/9-2/9) = 7 + 7/9 = 7 7/9

3. 1/9х + 7/18х - 13/27х = 1 5/6

6/54х + 21/54х - 26/54х = 1 5/6

1/54х = 1 5/6

х = 1 5/6 : 1/54 = 11/6 * 54/1 = 11 * 9 = 99;    х = 99.

4. Пропорция: творение средних членов одинаково творению крайних:

а) х : 2,1 = 1/3 : 0,35         б) х : 7/8 = 2/3 : 18/37       в) 3 1/12 : х = 5 4/7 : 18/37

х * 0,35 = 2,1 * 1/3             х * 18/37 = 7/8 * 2/3          х * 5 4/7 = 3 1/12 * 18/37

0,35х = 21/10 * 1/3            18/37х = 14/24                  5 4/7х = 37/12 * 18/37

х = 21/30 : 35/10                х = 14/24 : 18/37              х = 18/12 : 39/4

х = 21/30 * 10/35                х = 14/24 * 37/18              х = 18/12 * 4/39

х = 21/105 = 1/5                  х = 259/216= 1 43/216     х = 18/117

5. 4 23/25 + х = 3 11/25 + 2 13/25

х = 5 24/25 - 4 23/25 = 1 1/25 = 1,04

6. а) 3/5 = 6/10 = 0,6;  б) 1/25 = 4/100 = 0,04;  в) 17/25 = 68/100 = 0,68;  г) 23/50 = 46/100 = 0,46;  д) 3/8 = 375/1000 = 0,375;  е) 7/20 = 35/100 = 0,35.