Let's solve each of these
mental addition problems step by step. These are designed to help students practice adding numbers quickly in their heads, often using strategies like rounding, breaking numbers apart, or recognizing number pairs that make 100.
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(a) 10 + 90 =
- Think: 10 + 90 = 100
✔ Answer: 100
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(b) 30 + 70 =
- Think: 30 + 70 = 100
✔ Answer: 100
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(c) 45 + 55 =
- Think: 45 + 55 = (40 + 50) + (5 + 5) = 90 + 10 = 100
✔ Answer: 100
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(d) 20 + 60 =
- Think: 20 + 60 = 80
✔ Answer: 80
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(e) 65 + 35 =
- Think: 65 + 35 = (60 + 30) + (5 + 5) = 90 + 10 = 100
✔ Answer: 100
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(f) 85 + 5 =
- Think: 85 + 5 = 90
✔ Answer: 90
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(g) 10 + 50 =
- Think: 10 + 50 = 60
✔ Answer: 60
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(h) 25 + 75 =
- Think: 25 + 75 = 100 (because 25 and 75 make a whole hundred)
✔ Answer: 100
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(i) 60 + 40 =
- Think: 60 + 40 = 100
✔ Answer: 100
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(j) 95 + 5 =
- Think: 95 + 5 = 100
✔ Answer: 100
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(k) 13 + 67 =
- Think: Break it down: 10 + 60 = 70, and 3 + 7 = 10 → 70 + 10 = 80
Or: 13 + 67 = (13 + 60) + 7 = 73 + 7 = 80
✔ Answer: 80
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(l) 54 + 46 =
- Think: 50 + 40 = 90, and 4 + 6 = 10 → 90 + 10 = 100
Or: 54 + 46 = 100 (they add up to 100)
✔ Answer: 100
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✔ Final Answers:
(a) 100
(b) 100
(c) 100
(d) 80
(e) 100
(f) 90
(g) 60
(h) 100
(i) 100
(j) 100
(k) 80
(l) 100
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💡
Tip for Mental Addition: Look for combinations that make 100, or break numbers into tens and ones. This helps speed up mental math!
Let me know if you'd like a printable version or explanation with visuals!
Parent Tip: Review the logic above to help your child master the concept of addition worksheet free third grade.
