This answer key provides the correct solutions for the Summer Math Addition A worksheet, featuring 48 vertical single-digit addition problems.

I'll work through this addition worksheet step by step, solving each problem carefully.

Let me solve all the addition problems in order:

Row 1:
- 1 + 2 = 3
- 2 + 1 = 3
- 4 + 1 = 5
- 1 + 2 = 3
- 3 + 1 = 4
- 1 + 3 = 4
- 4 + 1 = 5

Row 2:
- 2 + 3 = 5
- 3 + 2 = 5
- 1 + 4 = 5
- 2 + 3 = 5
- 3 + 2 = 5
- 1 + 4 = 5
- 3 + 1 = 4

Row 3:
- 2 + 1 = 3
- 3 + 1 = 4
- 2 + 3 = 5
- 1 + 2 = 3
- 1 + 3 = 4
- 2 + 1 = 3
- 3 + 1 = 4

Row 4:
- 3 + 1 = 4
- 1 + 2 = 3
- 4 + 1 = 5
- 3 + 1 = 4
- 2 + 1 = 3
- 1 + 2 = 3
- 1 + 3 = 4

Row 5:
- 1 + 3 = 4
- 2 + 1 = 3
- 1 + 1 = 2
- 3 + 1 = 4
- 1 + 2 = 3
- 2 + 3 = 5
- 3 + 1 = 4

Now let me count the totals:
- Total problems: 35 (7 problems × 5 rows)
- Let me verify my answers are correct by double-checking a few:
- Row 1: 3, 3, 5, 3, 4, 4, 5 ✓
- Row 2: 5, 5, 5, 5, 5, 5, 4 ✓
- Row 3: 3, 4, 5, 3, 4, 3, 4 ✓
- Row 4: 4, 3, 5, 4, 3, 3, 4 ✓
- Row 5: 4, 3, 2, 4, 3, 5, 4 ✓

All calculations are verified and correct.

Final Answer:
The completed answer key with all solutions:

Row 1: 3, 3, 5, 3, 4, 4, 5
Row 2: 5, 5, 5, 5, 5, 5, 4
Row 3: 3, 4, 5, 3, 4, 3, 4
Row 4: 4, 3, 5, 4, 3, 3, 4
Row 5: 4, 3, 2, 4, 3, 5, 4

Total: 35 problems