№37
В часу 60 мин
3 мин = 3/60 = 1/20
20 мин = 20/60 = 1/3
48 мин = 48/60 = 4/5
50 мин = 50/60 = 5/6
№ 38.
развёрнутый угол 180°
9° = 9/180 = 1/20
10° = 10/180 = 1/18
36° = 36/180 = 1/5
84° = 84/180 = 21/45
№39.
7/15 + 2/15 = 9/15 = 3/5
37/46 - 21/46 = 16/46 = 8/23
5ц 17/36 + 3ц 7/36 = 8ц 34/36 = 8ц 2/3
17ц 53/63 - 9ц 32/63 = 8ц 21/63 = 8ц 3/21
№ 40
9 * 16 1 * 2 2
-------- = -------- = -------
8 * 27 1 * 3 3
8 * 28 2 * 4 8
--------- = ----------- = -----
35 * 12 5 * 3 15
2 * 3 * 5 1 * 1 * 1 1
------------- = -------------- = -----
4 * 9 * 25 2 * 3 * 5 30
7 * 13 - 7 * 2 1 * 13 - 1 * 1 13 - 1 12 6
------------------- = ------------------ = ---------- = ------ = -------
35 * 9 + 35 * 2 5 * 9 + 5 * 1 45 + 5 50 25