№ 1.
20/25 = 20: 5 / 25 : 5 = 4/5
36/72 = 36 : 36 / 72 : 36 = 1/2
105/30 = 3 15/30 = 3 15: 15 / 30 : 15 = 3 1/2
№ 2
8/15 < 7/12 = 32/60 и 35/60 , т.к. 35 > 32, то 8/15 < 7/12
11/303 > 7/202 = 22/606 и 21/606, т.. 22 > 21, то 11/303 > 7/202
№ 3
3/4 - 1/6 = 9/12 - 2/12 = 7/12
11/12 + 9/10 = 55/60 + 54/60 = 109/60 = 1 49/60
5/6 + 3/8 - 1/3 = 20/24 + 9/24 - 8/24 = 21/24 = 21 : 3/24 : 3 = 7/8
№ 4
1) 4/15 - 1/12 = 16/60 - 5/60 = 11/60 прошла за 2-ые сутки
2) 4/15 + 11/60 = 16/60 + 11/60 = 27/60 = 9/20 всего прошла за два дня лодка
№ 5
8/11> 4/6 ; 2/3; 5/7; 6/9 > 7/11
№ 6
504 = 2 * 2 * 2 * 3 * 3 * 7 = 2³ * 3² * 7
756 = 2 * 2 * 3 * 3 * 3 * 7 = 2² * 3³ * 7
НОД (504 и 756) = 2² * 3² * 7 = 4 * 9 * 7 = 252
НОК (504 и 756) = 2³ * 3³ * 7 = 8 * 27 * 7 = 1512
№ 7
226,8 : 0,54 + 4,46 * 14 = 420 + 62,44 = 482,44