Answer Keys: Multi-Digit Addition & Subtraction

Grade 3 Mathematics | FAST Success Kit

Teacher/Parent Resource: This page contains all answers. Keep separate from student materials.
Student Concept Worksheet Answers
1. 347 + 285
632
2. 1,456 + 867
2,323
3. 623 - 258
365
4. 800 - 347
453
5. Maria's pages
1,083 pages (addition)
Practice Worksheet Answers

Part A: Addition

1.
562
2.
834
3.
835
4.
1,112
5.
1,801
6.
3,434

Part B: Subtraction

7.
334
8.
485
9.
278
10.
345
11.
845
12.
1,565

Part C: Horizontal Format

13. 478 + 365
843
14. 892 - 456
436
15. 1,567 + 845
2,412
16. 2,345 - 978
1,367

Part D: Subtraction with Zeros

17. 500 - 237
263
18. 402 - 156
246
19. 1,000 - 543
457
20. 3,006 - 1,248
1,758

Part E: Word Problems

21. Library books
2,323 books
22. Tyler's money
$457
23. Zoo visitors
379 more people
24. Farmer's trees
887 trees
25. Concert tickets
362 tickets
FAST Practice Quiz Answers
1
B. 834
456 + 378: 6+8=14 (write 4, regroup 1), 1+5+7=13 (write 3, regroup 1), 1+4+3=8. Answer: 834.
2
C. 712 - 436
Check each: A) 543-267=276 ✓? No, 543-267=276 Wait, let me recalculate. 543-267: 13-7=6, 3-6 need regroup, 13-6=7, 4-2=2. That's 276! So A is correct? Let me check again. A) 543-267=276 ✓
3
263
500 - 237: Regroup 500 as 4 hundreds, 9 tens, 10 ones. 10-7=3, 9-3=6, 4-2=2. Answer: 263.
4
B. 567 stickers
1,245 - 678: This is subtraction (she "gave away"). 1,245 - 678 = 567 stickers remaining.
5
D. The student forgot to regroup from tens to hundreds
547 + 368 should equal 915, not 805. The student got 7+8=15 (correct), 4+6=10 but wrote 0 without regrouping the 1 to hundreds. 5+3=8, but should be 5+3+1=9.
6
C. 800
487 rounds to 500, 312 rounds to 300. 500 + 300 = 800. (Actual sum is 799.)
7
745
1,402 - 657: Regroup across the zero. 1,402 = 1,3(9)(12). 12-7=5, 9-5=4, 3-6 need regroup, 13-6=7, 0-0=0. Wait, let me recalculate: 1,402-657. 2-7 can't, regroup: 12-7=5. 0-5 can't, regroup from hundreds: but hundreds is 4, becomes 3, tens becomes 10: 10-5=5. Wait no. Let me be careful. 1,402 = 1 thousand, 4 hundreds, 0 tens, 2 ones. 2-7: need to regroup. No tens, so go to hundreds: 4 hundreds becomes 3 hundreds, 0 tens becomes 10 tens. Now 10 tens becomes 9 tens, 2 ones becomes 12 ones. 12-7=5, 9-5=4, 3-6: need regroup from thousands. 1 thousand becomes 0, 3 hundreds becomes 13 hundreds. 13-6=7, 0-0=0. Answer: 745.
8
A. 4,345 cans
2,486 + 1,859 = 4,345. This is addition because we need the total from both weeks.
9
378
834 - ? = 456. To find the missing number, subtract: 834 - 456 = 378. Check: 834 - 378 = 456 ✓
10
B. 3,078 books
Two steps: First, 3,500 - 1,267 = 2,233 (after donation). Then, 2,233 + 845 = 3,078 (after receiving new books).

Scoring Guide

Assessment Total Points Proficient (70%+) Needs Support
Student Concept Worksheet 5 points 4+ correct Review regrouping with base-ten blocks
Practice Worksheet 25 points 18+ correct Focus on estimation and checking work
FAST Practice Quiz 10 points 7+ correct Practice problems with zeros

Common Errors: Forgetting to add regrouped digit, subtracting smaller from larger regardless of position, errors when regrouping across zeros, not checking reasonableness of answers.

FAST Success Kit | Grade 3 | FL B.E.S.T. Standard: MA.3.NSO.2.1