Выполните умножение: 1) 316 · 43; 2) 607 · 78; 3) 4 321 · 42; 4) 3 236 · 840; 5) 2 821 · 538; 6) 408 · 205.

1. \(316 \cdot 43 = 316 \cdot (40 + 3) = 12\,640 + 948 = 13\,588\).
2. \(607 \cdot 78 = 607 \cdot (80 - 2) = 48\,560 - 1\,214 = 47\,346\).
3. \(4\,321 \cdot 42 = 4\,321 \cdot (40 + 2) = 172\,840 + 8\,642 = 181\,482\).
4. \(3\,236 \cdot 840 = 3\,236 \cdot 84 \cdot 10 = (258\,880 + 12\,944) \cdot 10 = 2\,718\,240\).
5. \(2\,821 \cdot 538 = 1\,410\,500 + 84\,630 + 22\,568 = 1\,517\,698\).
6. \(408 \cdot 205 = 408 \cdot (200 + 5) = 81\,600 + 2\,040 = 83\,640\).

Ответ: 1) 13 588; 2) 47 346; 3) 181 482; 4) 2 718 240; 5) 1 517 698; 6) 83 640.