You're working on
Mental Addition of 2-Digit Numbers, and the worksheet gives a helpful tip:
> *“When you are adding in your head, it is usually easiest to start with the bigger number first and then add the smaller number.”*
This is a great mental math strategy! It reduces cognitive load — starting with the larger number means you’re adding a smaller amount to it, which feels more intuitive.
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Let’s solve all 30 problems step-by-step using
mental addition techniques (like breaking numbers into tens and ones, or using “make a ten” strategies). I’ll show the reasoning for a few, then list all answers.
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🧠 Mental Math Strategy Recap:
1.
Start with the bigger number (as suggested).
2.
Break the smaller number into tens and ones.
3.
Add the tens first, then the ones.
4.
Use compensation or rounding if helpful (e.g., 87 + 15 → 87 + 10 = 97, then +5 = 102).
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✔ Solved Problems with Explanations:
#### 1) 57 + 38
→ Start with 57. Add 30 → 87. Then add 8 →
95
#### 2) 62 + 35
→ 62 + 30 = 92, +5 =
97
#### 3) 87 + 15
→ 87 + 10 = 97, +5 =
102
#### 4) 37 + 65
→ Start with 65 (bigger), +30 = 95, +7 =
102
#### 5) 55 + 65
→ 65 + 50 = 115, +5 =
120
#### 6) 82 + 51
→ 82 + 50 = 132, +1 =
133
#### 7) 76 + 45
→ 76 + 40 = 116, +5 =
121
#### 8) 57 + 62
→ 62 + 50 = 112, +7 =
119
#### 9) 39 + 71
→ 71 + 30 = 101, +9 =
110
#### 10) 84 + 33
→ 84 + 30 = 114, +3 =
117
#### 11) 56 + 47
→ 56 + 40 = 96, +7 =
103
#### 12) 37 + 62
→ 62 + 30 = 92, +7 =
99
#### 13) 75 + 43
→ 75 + 40 = 115, +3 =
118
#### 14) 80 + 56
→ 80 + 50 = 130, +6 =
136
#### 15) 43 + 38
→ 43 + 30 = 73, +8 =
81
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#### 16) 83 + 24
→ 83 + 20 = 103, +4 =
107
#### 17) 65 + 57
→ 65 + 50 = 115, +7 =
122
#### 18) 42 + 63
→ 63 + 40 = 103, +2 =
105
#### 19) 83 + 84
→ 84 + 80 = 164, +3 =
167
#### 20) 74 + 29
→ 74 + 20 = 94, +9 =
103
#### 21) 94 + 45
→ 94 + 40 = 134, +5 =
139
#### 22) 77 + 56
→ 77 + 50 = 127, +6 =
133
#### 23) 69 + 54
→ 69 + 50 = 119, +4 =
123
#### 24) 92 + 36
→ 92 + 30 = 122, +6 =
128
#### 25) 89 + 76
→ 89 + 70 = 159, +6 =
165
#### 26) 68 + 45
→ 68 + 40 = 108, +5 =
113
#### 27) 72 + 67
→ 72 + 60 = 132, +7 =
139
#### 28) 48 + 95
→ 95 + 40 = 135, +8 =
143
#### 29) 64 + 86
→ 86 + 60 = 146, +4 =
150
#### 30) 87 + 93
→ 93 + 80 = 173, +7 =
180
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📋 Final Answer Key:
1)
95
2)
97
3)
102
4)
102
5)
120
6)
133
7)
121
8)
119
9)
110
10)
117
11)
103
12)
99
13)
118
14)
136
15)
81
16)
107
17)
122
18)
105
19)
167
20)
103
21)
139
22)
133
23)
123
24)
128
25)
165
26)
113
27)
139
28)
143
29)
150
30)
180
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✔ You can now fill these in on your worksheet!
💡
Pro Tip: To check your work mentally, try reversing the order (add the smaller number first) — the sum should be the same. Or use estimation: e.g., 87 + 93 ≈ 90 + 90 = 180 — matches our answer!
Let me know if you’d like to practice any of these with voice or visual breakdowns!
Parent Tip: Review the logic above to help your child master the concept of mental addition worksheet.
