(printed) 320,000,000

648 ÷ 8 = 81

700 million

2,530,000,000

four billion eight hundred million

10,000 times. 100 million → 1 billion → 10 billion → 100 billion → 1 trillion: four more zeros.

936 ÷ 4 = 234

725 ÷ 6 = 120 remainder 5. Check he did not skip the 0 in the ones place.

84 x 7 = 588

500 million (500,000,000) is bigger. 50 million is 50,000,000 — one zero fewer.

250 ÷ 6 = 41 bags, 4 left over

512 ÷ 8 = 64

45 ÷ 7 = 6 teams, 3 left over

150 ÷ 8 = 18 each, 6 left over

350 ÷ 9 = 38 remainder 8 → 39 pages.

If he answers 38, that is the whole point of the question. The 8 left over still need a page. A remainder sometimes means rounding up.

12,000 ÷ 30 = 400 yen

48,000 ÷ 6 = 8,000 people per km²

387 → the ones digit is 7, which is 5 or more, so round up → 390

October's 'rounding' starts here. Not knowing it yet is fine.

4926 → the tens digit is 2, which is 4 or less, so round down → 4900

4 x 15 + 3 = 63. It comes back to the number we started with, so it is right.

6 x 47 + 2 = 284