выполните действия: 3/8*4/5:9/10; 6/7:3/5*1 цел2/5.

Выполним действия, умножение и деление по очереди:

1. 3/8 * 4/5 : 9/10 = 1/3;

1) 3/8 * 4/5 = (3 * 4) / (8 * 5) = (3 * 4) / (2 * 4 * 5) = 3 / (2 * 5) = 3/10;

2) 3/10 : 9/10 = 3/10 * 10/9 = (3 * 10) / (10 * 9) = (3 * 10) / (10 * 3 * 3) = 1/3.

2. 6/7 : 3/5 * 1 2/5 = 2;

1) 6/7 : 3/5 = 6/7 * 5/3 = (6 * 5) / (7 * 3) = (3 * 2 * 5) / (7 * 3) = (2 * 5) / 7 = 10/7 = 1 3/7;

2) 1 3/7 * 1 2/5 = 10/7 * (1 * 5 + 2) / 5 = 10/7 * 7/5 = (10 * 7) / (7 * 5) = (5 * 2 * 7) / (7 * 5) = 2.