А)2/3*1 2/7 б)3 1/8*2 в) 1 1/7*1 3/4 г) 5/6:2 2/9 д) 3 3/5:1 9/10 а) 2 1/2*1 1/5-2 2/15:2 б) 4 3/7*8 4/9-4 3/7 *6 4/9

Чтобы выполнить действия, представим дроби в виде неправильных:

1) 2/3 * 1 2/7 = 2/3 * 9/7 = (2 * 3 * 3)/(3 * 7) = 6/7;

2) 3 1/8 * 2 = 25/8 * 2 = (25 * 2)/(4 * 2) = 25/4 = 6 1/4;

3) 1 1/7 * 1 3/4 = 8/7 * 7/4 = (4 * 2 * 7)/(7 * 4) = 2;

4) 5/6 : 2 2/9 = 5/6 : 20/8 = 5/6 * 8/20 = (5 * 2 * 4)/(2 * 3 * 5 * 4) = 1/3;

5) 3 3/5 : 1 9/10 = 18/5 : 19/10 = 18/5 * 10/19 = (18 * 5 * 2)/(5 * 19) = 36/19 = 1 17/19;

6) 2 1/2 * 1 1/5 - 2 2/15 : 2 = 5/2 * 6/5 - 32/15 * 1/2 = (5 * 2 * 3)/(2 * 5) - (16 * 2)/(15 * 2) = 3 - 16/15 = 3 - 1 1/15 = 1 14/15;

7) 4 3/7 * 8 4/9 - 4 3/7 * 6 4/9 = 31/7 * 76/9 - 31/7 * 58/9 = (31 * 76 - 31 * 58)/63 = (31 * (76 - 58))/63 = (31 * 18)/63 = (31 * 9 * 2)/(7 * 9) = (31 * 2)/7 = 62/7 = 8 6/7;

8) 1 2/9 * 1 2/11 * 1 2/13 * 1 2/15 * 1 2/17 * 1 2/19 = 11/9 * 13/11 * 15/13 * 17/15 * 19/17 * 21/19 = 21/9 = 2 3/9 = 2 1/3.