Answer key for a math addition worksheet with problems involving numbers 1 to 4.

To solve this worksheet, we need to add the two numbers in each column. The top number is the ones place, and the bottom number is also in the ones place. We will add them together to get the sum for each problem.

Let's go through the problems row by row, from left to right.

Row 1:
1. $1 + 2 = 3$
2. $2 + 3 = 5$
3. $1 + 4 = 5$
4. $2 + 1 = 3$
5. $1 + 2 = 3$
6. $3 + 3 = 6$
7. $1 + 4 = 5$
8. $2 + 1 = 3$

Row 2:
9. $2 + 3 = 5$
10. $1 + 3 = 4$
11. $2 + 4 = 6$
12. $1 + 3 = 4$
13. $2 + 3 = 5$
14. $3 + 4 = 7$
15. $1 + 3 = 4$
16. $2 + 4 = 6$

Row 3:
17. $2 + 1 = 3$
18. $3 + 3 = 6$
19. $1 + 4 = 5$
20. $2 + 3 = 5$
21. $1 + 2 = 3$
22. $3 + 3 = 6$
23. $1 + 3 = 4$
24. $3 + 4 = 7$

Row 4:
25. $3 + 1 = 4$
26. $1 + 4 = 5$
27. $2 + 1 = 3$
28. $3 + 4 = 7$
29. $1 + 4 = 5$
30. $2 + 1 = 3$
31. $1 + 4 = 5$
32. $2 + 1 = 3$

Row 5:
33. $1 + 3 = 4$
34. $2 + 1 = 3$
35. $1 + 4 = 5$
36. $3 + 1 = 4$
37. $1 + 2 = 3$
38. $2 + 3 = 5$
39. $1 + 3 = 4$
40. $3 + 4 = 7$

Here are the answers filled in for each position on the sheet:

Row 1 Answers: 3, 5, 5, 3, 3, 6, 5, 3
Row 2 Answers: 5, 4, 6, 4, 5, 7, 4, 6
Row 3 Answers: 3, 6, 5, 5, 3, 6, 4, 7
Row 4 Answers: 4, 5, 3, 7, 5, 3, 5, 3
Row 5 Answers: 4, 3, 5, 4, 3, 5, 4, 7

Final Answer:
The completed sums for the worksheet are:

Row 1: 3, 5, 5, 3, 3, 6, 5, 3
Row 2: 5, 4, 6, 4, 5, 7, 4, 6
Row 3: 3, 6, 5, 5, 3, 6, 4, 7
Row 4: 4, 5, 3, 7, 5, 3, 5, 3
Row 5: 4, 3, 5, 4, 3, 5, 4, 7