Let’s solve each problem step by step using the open number line method shown in example #1.
We start at the first number, then add tens and ones separately — just like jumping forward on a number line.
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Problem 2: 52 + 36
Start at 52.
Add 30 (three jumps of 10):
→ 52 + 10 = 62
→ 62 + 10 = 72
→ 72 + 10 = 82
Now add 6 (six jumps of 1):
→ 82 + 1 = 83
→ 83 + 1 = 84
→ 84 + 1 = 85
→ 85 + 1 = 86
→ 86 + 1 = 87
→ 87 + 1 = 88
Final sum:
88
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Problem 3: 43 + 28
Start at 43.
Add 20 (two jumps of 10):
→ 43 + 10 = 53
→ 53 + 10 = 63
Now add 8 (eight jumps of 1):
→ 63 + 1 = 64
→ 64 + 1 = 65
→ 65 + 1 = 66
→ 66 + 1 = 67
→ 67 + 1 = 68
→ 68 + 1 = 69
→ 69 + 1 = 70
→ 70 + 1 = 71
Final sum:
71
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Problem 4: 79 + 15
Start at 79.
Add 10 (one jump of 10):
→ 79 + 10 = 89
Now add 5 (five jumps of 1):
→ 89 + 1 = 90
→ 90 + 1 = 91
→ 91 + 1 = 92
→ 92 + 1 = 93
→ 93 + 1 = 94
Final sum:
94
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Problem 5: 64 + 33
Start at 64.
Add 30 (three jumps of 10):
→ 64 + 10 = 74
→ 74 + 10 = 84
→ 84 + 10 = 94
Now add 3 (three jumps of 1):
→ 94 + 1 = 95
→ 95 + 1 = 96
→ 96 + 1 = 97
Final sum:
97
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Problem 6: 87 + 11
Start at 87.
Add 10 (one jump of 10):
→ 87 + 10 = 97
Now add 1 (one jump of 1):
→ 97 + 1 = 98
Final sum:
98
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Problem 7: 58 + 24
Start at 58.
Add 20 (two jumps of 10):
→ 58 + 10 = 68
→ 68 + 10 = 78
Now add 4 (four jumps of 1):
→ 78 + 1 = 79
→ 79 + 1 = 80
→ 80 + 1 = 81
→ 81 + 1 = 82
Final sum:
82
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Final Answer:
2. 88
3. 71
4. 94
5. 97
6. 98
7. 82
Parent Tip: Review the logic above to help your child master the concept of open number line worksheet.
