Условие:

(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

8 * 4 * 25 * 5 = (4 * 25) * (8 * 5) = 100 * 40 = 4000
9 * 15 * 6 * 10 = (15 * 6) * (9 * 10) = 90 * 90 = 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 = (6 * 5) * (35 * 2) = 30 * 70 = 2100