Выполните умножение 1.4 1/6x2 2/5; 2.2 1|10*2 1|7; 3.1 7|8*2 2|5,4.2 2/21 * 3/12

Первый пример.

4 1/6 * 2 2/5 = 4 * 6 + 1/6 * 2 * 5 + 2/5 = 25/6 * 12/5 = 25 * 12/6 * 5 = 300/30 = 10 * 30/1 * 30 = 10/1 = 10;

Второй пример.

2 1/10 * 2 1/7 = 2 * 10 + 1/10 * 2 * 7 + 1/7 = 21/10 * 15/7 = 21 * 15/10 * 7 = 315/70 = 9 * 35/2 * 35 = 9/2 = 1 + 4 * 2/2 = 4 1/2;

Третий пример.

1 7/8 * 2 2/5 = 1 * 8 + 7/8 * 2 * 5 + 2/5 = 15/8 * 12/5 = 15 * 12/8 * 5 = 180/40 = 9 * 20/2 * 20 = 9/2 = 1 + 4 * 2/2 = 4 1/2;

Четвертый пример.

2 2/21 * 3/12 = 2 * 21 + 2/21 * 3/12 = 44/21 * 3/12 = 44 * 3/21 * 12 = 132/252 = 11 * 12/21 * 12 = 11/21;