Three-Digit Addition & Subtraction — Answer Key
Part A: Multiple Choice
Circle the best answer for each question.
1. A store had 465 toys. They sold 187 in the morning and 134 in the afternoon. How many toys are left?
A) 134
B) 144
C) 154
D) 244
476 - 332 = 144. Subtract ones: 6 - 2 = 4. Subtract tens: 7 - 3 = 4. Subtract hundreds: 4 - 3 = 1.
2. What is the best estimate for 389 + 512 when both numbers are rounded to the nearest hundred?
A) 800
B) 900
C) 1000
D) 700
456 rounds to 500 and 448 rounds to 400, so 500 + 400 = 900.
3. Sam has 723 baseball cards. He gives 258 to his friend and then gets 175 new ones. How many does he have now?
A) 540
B) 640
C) 650
D) 740
385 rounds to 390 and 257 rounds to 250, so 390 + 250 = 640.
4. Which subtraction problem requires borrowing in both the ones and tens places?
A) 876 - 543
B) 654 - 278
C) 999 - 111
D) 735 - 214
654 - 278 = 376. This is the subtraction problem that results in 376.
Part B: Fill in the Blank
Write the correct answer on each line.
1. 347 + 286 + 158 = 791.
347 + 286 = 633, then 633 + 158 = 791.
2. A library has 925 books. If 368 are checked out, 557 books remain.
925 - 368 = 557. Subtract ones: 15 - 8 = 7 (borrow from tens). Subtract tens: 1 - 6 requires borrowing: 11 - 6 = 5. Subtract hundreds: 8 - 3 = 5.
3. 600 - 247 = 353.
600 - 247 = 353. Borrow across zeros: 600 becomes 5-9-10. Subtract ones: 10 - 7 = 3. Subtract tens: 9 - 4 = 5. Subtract hundreds: 5 - 2 = 3.
4. The sum of 489 and 376 is 865.
489 + 376 = 865. Add ones: 9 + 6 = 15, write 5 carry 1. Add tens: 8 + 7 + 1 = 16, write 6 carry 1. Add hundreds: 4 + 3 + 1 = 8.
5. 1000 - 637 = 363.
1000 - 637 = 363. Borrow across zeros: subtract ones: 10 - 7 = 3. Subtract tens: 9 - 3 = 6. Subtract hundreds: 9 - 6 = 3.