1) на 2:
1/2 * 2 = 2/2 = 1,
2) на 1 2/5:
5/7 * 1 2/5 = 5/7 * 7/5 = 35/35 = 1,
3) на 1/4:
4 * 1/4 = 4/4 = 1,
4) на 1/11:
11 * 1/11 = 11/11 = 1,
5) на 3/10:
3 1/3 * 3/10 = 10/3 * 3/10 = 30/30 = 1,
6) на 5/27:
5 2/5 * 5/27 = 27/5 * 5/27 = 135/135 = 1,
7) на - 1/7:
-7 * (-1/7) = 7/7 = 1,
8) на - 1 4/5:
-5/9 * (-1 4/5) = - 5/9 * (-9/5) = 45/45 = 1