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

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.