4. Вычисли: 238 × 40; 780 × 500; 3800 × 90; 9400 × 800; 640 000 : 800; 300 000 : 6000; 35 : 8; 49 : 6.

1. \(238 \times 40 = 238 \times 4 \times 10 = 952 \times 10 = 9520\).
2. \(780 \times 500 = 780 \times 5 \times 100 = 3900 \times 100 = 390000\).
3. \(3800 \times 90 = 38 \times 9 \times 1000 = 342 \times 1000 = 342000\).
4. \(9400 \times 800 = 94 \times 8 \times 10000 = 752 \times 10000 = 7520000\).
5. \(640000 : 800 = 6400 : 8 = 800\).
6. \(300000 : 6000 = 300 : 6 = 50\).
7. \(35 : 8 = 4\) (ост. \(3\)).
8. \(49 : 6 = 8\) (ост. \(1\)).

Ответ: 9520; 390000; 342000; 7520000; 800; 50; 4 (ост. 3); 8 (ост. 1).