Mental math practice sheet for adding and subtracting 10 and 100 from three-digit numbers.

Let’s work through this step by step.

We have a table with 6 numbers in the first column:
367, 785, 689, 890, 243, 338

For each number, we need to do four things:
- Add 10
- Subtract 10
- Add 100
- Subtract 100

Let’s go row by row.

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Row 1: 367

- Add 10 → 367 + 10 = 377
- Subtract 10 → 367 - 10 = 357
- Add 100 → 367 + 100 = 467
- Subtract 100 → 367 - 100 = 267

✔ Check: All look right.

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Row 2: 785

- Add 10 → 785 + 10 = 795
- Subtract 10 → 785 - 10 = 775
- Add 100 → 785 + 100 = 885
- Subtract 100 → 785 - 100 = 685

✔ Check: Correct.

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Row 3: 689

- Add 10 → 689 + 10 = 699
- Subtract 10 → 689 - 10 = 679
- Add 100 → 689 + 100 = 789
- Subtract 100 → 689 - 100 = 589

✔ Check: Good.

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Row 4: 890

- Add 10 → 890 + 10 = 900
- Subtract 10 → 890 - 10 = 880
- Add 100 → 890 + 100 = 990
- Subtract 100 → 890 - 100 = 790

✔ Check: All correct.

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Row 5: 243

- Add 10 → 243 + 10 = 253
- Subtract 10 → 243 - 10 = 233
- Add 100 → 243 + 100 = 343
- Subtract 100 → 243 - 100 = 143

✔ Check: Right.

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Row 6: 338

- Add 10 → 338 + 10 = 348
- Subtract 10 → 338 - 10 = 328
- Add 100 → 338 + 100 = 438
- Subtract 100 → 338 - 100 = 238

✔ Check: All good.

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Now, let’s compile all answers into the table format as requested.

Final Answer:

| | ADD 10 | SUBTRACT 10 | ADD 100 | SUBTRACT 100 |
|-------|--------|-------------|---------|--------------|
| 367 | 377 | 357 | 467 | 267 |
| 785 | 795 | 775 | 885 | 685 |
| 689 | 699 | 679 | 789 | 589 |
| 890 | 900 | 880 | 990 | 790 |
| 243 | 253 | 233 | 343 | 143 |
| 338 | 348 | 328 | 438 | 238 |