Three-Digit Addition & Subtraction — Answer Key
Part A: Fix the Sentence
Each sentence has an error. Rewrite it correctly on the line.
1. Fix the sentence:
345 + 278 = 513.
Corrected: 345 + 278 = 623 because 5 + 8 = 13, carry 1, then 4 + 7 + 1 = 12, carry 1, then 3 + 2 + 1 = 6.
The corrected sentence is: "345 + 278 = 623 because 5 + 8 = 13, carry 1, then 4 + 7 + 1 = 12, carry 1, then 3 + 2 + 1 = 6.". The original sentence "345 + 278 = 513." contained an error that needed to be fixed.
2. Fix the sentence:
156 + 237 = 383.
Corrected: 156 + 237 = 393 because 5 + 3 = 8, not 7, so the tens digit should be 9.
The corrected sentence is: "156 + 237 = 393 because 5 + 3 = 8, not 7, so the tens digit should be 9.". The original sentence "156 + 237 = 383." contained an error that needed to be fixed.
3. Fix the sentence:
489 + 234 = 613.
Corrected: 489 + 234 = 723 because 9 + 4 = 13, carry 1, then 8 + 3 + 1 = 12, carry 1, then 4 + 2 + 1 = 7.
The corrected sentence is: "489 + 234 = 723 because 9 + 4 = 13, carry 1, then 8 + 3 + 1 = 12, carry 1, then 4 + 2 + 1 = 7.". The original sentence "489 + 234 = 613." contained an error that needed to be fixed.
Part B: Fill in the Blank
Write the missing word or number on each line.
1. 247 + 135 = 382.
247 + 135 = 382. Add ones: 7 + 5 = 12, write 2 carry 1. Add tens: 4 + 3 + 1 = 8. Add hundreds: 2 + 1 = 3.
2. 368 + 214 = 582.
368 + 214 = 582. Add ones: 8 + 4 = 12, write 2 carry 1. Add tens: 6 + 1 + 1 = 8. Add hundreds: 3 + 2 = 5.
3. 153 + 429 = 582.
153 + 429 = 582. Add ones: 3 + 9 = 12, write 2 carry 1. Add tens: 5 + 2 + 1 = 8. Add hundreds: 1 + 4 = 5.
4. 276 + 518 = 794.
276 + 518 = 794. Add ones: 6 + 8 = 14, write 4 carry 1. Add tens: 7 + 1 + 1 = 9. Add hundreds: 2 + 5 = 7.
Part C: True or False?
Read each statement. Circle True or False.
1. When adding 567 + 245, you need to regroup in the ones place because 7 + 5 = 12.
True False
The statement is true based on the addition calculation.
2. 321 + 456 = 787.
True False
The statement is false; check the addition carefully.
3. The sum of 400 + 300 is 700.
True False
The statement is true based on the addition calculation.