Найди произведение: а) 2 целых 1/7*3 целых 1/9 б) 3/7*7/9 в) 5/8*1 целых 13/15*2 целых 2/7

Первый пример.

2 1/7 * 3 1/9 = 2 * 7 + 1/7 * 3 * 9 + 1/9 = 15/7 * 28/9 = 15 * 28/7 * 9 = 420/63 = 20 * 21/3 * 21 = 20/3 = 2 + 6 * 3/3 = 6 2/3;

Второй пример.

3/7 * 7/9 = 3 * 7/7 * 9 = 21/63 = 1 * 21/3 * 21 = 1/3;

Третий пример.

5/8 * 1 13/15 * 2 2/7 = 2 2/3;

Первое действие.

5/8 * 1 13/15 = 5/8 * 1 * 15 + 13/15 = 5/8 * 28/15 = 5 * 28/8 * 15 = 140/120 = 7 * 20/6 * 20 = 7/6 = 1 + 1 * 6/6 = 1 1/6;

Второе действие.

1 1/6 * 2 2/7 = 1 * 6 + 1/6 * 2 * 7 + 2/7 = 7/6 * 16/7 = 7 * 16/6 * 7 = 112/42 = 8 * 14/3 * 14 = 8/3 = 2 + 2 * 3/3 = 2 2/3.