Выполните умножения устно.
42 * 4
51 * 6
69 * 4
75 * 4
92 * 3
48 * 5
42 * 4 = 168
51 * 6 = 306
69 * 4 = 276
75 * 4 = 300
92 * 3 = 276
48 * 5 = 240
Вычисления:
42 * 4 = (40 + 2) * 4 = 40 * 4 + 2 * 4 = 4 * 4 * 10 + 2 * 4 = 16 * 10 + 8 = 160 + 8 = 168
51 * 6 = (50 + 1) * 6 = 50 * 6 + 1 * 6 = 5 * 6 * 10 + 1 * 6 = 30 * 10 + 6 = 300 + 6 = 306
69 * 4 = (60 + 9) * 4 = 60 * 4 + 9 * 4 = 6 * 4 * 10 + 9 * 4 = 24 * 10 + 36 = 240 + 36 = 276
75 * 4 = (70 + 5) * 4 = 7 * 4 * 10 + 5 * 4 = 28 * 10 + 20 = 280 + 20 = 300
92 * 3 = (90 + 2) * 3 = 9 * 3 * 10 + 2 * 3 = 27 * 10 + 6 = 270 + 6 = 276
48 * 5 = (40 + 8) * 5 = 4 * 5 * 10 + 8 * 5 = 20 * 10 + 40 = 200 + 40 = 240
