66. (Устно.) Вычисли удобным способом: 8 * 4 * 25 * 5 9 * 15 * 6 * 10 15 * 7 * 4 * 10 8 * 7 * 5 * 3 25 * 3 * 8 * 4 35 * 6 * 5 * 2

Решение: * 8 * 4 * 25 * 5 = (8 * 5) * (4 * 25) = 40 * 100 = 4000 * 9 * 15 * 6 * 10 = (9 * 6) * (15 * 10) = 54 * 150 = 8100 * 15 * 7 * 4 * 10 = (15 * 4) * (7 * 10) = 60 * 70 = 4200 * 8 * 7 * 5 * 3 = (8 * 5) * (7 * 3) = 40 * 21 = 840 * 25 * 3 * 8 * 4 = (25 * 4) * (3 * 8) = 100 * 24 = 2400 * 35 * 6 * 5 * 2 = (35 * 2) * (6 * 5) = 70 * 30 = 2100