Chapter 23
Answers
1. 140
The ones digit is 6, so round up by adding 1 to the tens digit (3 + 1 = 4) and changing the 6 to 0: 136 → 140.
2. 220
The ones digit is 4, so round down by changing the 4 to 0: 224 → 220.
3. 2,500
The tens digit is 9, so round up by adding 1 to the hundreds digit (4 + 1 = 5) and changing both the 9 and the 2 to 0s: 2,492 → 2,500.
4. 909,100
The tens digit is 9, so round up by adding 1 to the hundreds digit (0 + 1 = 1) and changing the 9 to 0: 909,090 → 909,100.
5. 9,000
The hundreds digit is 0, so round down by changing every digit to the right of the thousands digit to 0: 9,099 → 9,000.
6. 235,000,000
The hundred-thousands digit is 5, so round up by adding 1 to the millions digit (4 + 1 = 5) and changing every digit to the right of the millions digit to 0: 234,567,890 → 235,000,000.
7. 68
Stack the numbers and add the columns from right to left.
8. 266
Stack the numbers and add the columns from right to left.
9. 2,310
Stack the numbers and add the columns from right to left.
10. 9,343
Stack the numbers and add the columns from right to left.
11. 406,055
Stack the numbers and add the columns from right to left. ...