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. ...