Question 1: Calculate mentally: 47 + 32.

Answer: 79

Question 2: Add 56 and 27 using mental strategies. Show your working.

Answer: 56 + 27 = 56 + (20 + 7) = (56 + 20) + 7 = 76 + 7 = 83

Question 3: Estimate the sum of 68 and 29 by rounding to the nearest ten. Then find the actual total.

Answer: Estimate: 70 + 30 = 100; Actual: 68 + 29 = 97

Question 4: Use a mental strategy to find 45 + 38.

Answer: 45 + 38 = (45 + 40) - 2 = 85 - 2 = 83

Question 5: Add 66 and 25 using mental addition. Explain your method.

Answer: Add 66 + 25 by breaking down 25 into 25 = 20 + 5. Then 66 + 20 = 86, and 86 + 5 = 91.

Question 6: Calculate 52 + 47 using a mental strategy that makes the calculation easier.

Answer: 52 + 47 = (50 + 2) + (50 - 3) = (50 + 50) + (2 - 3) = 100 - 1 = 99

Question 7: What is 59 + 33? Use a mental method and explain it briefly.

Answer: Add 59 + 33 by rounding 33 to 40 and adjusting: 59 + 40 = 99, then subtract 7 (since 40 was 7 too many), so 99 - 7 = 92.

Question 8: Add 68 and 29 by rounding to the nearest ten and adjusting.

Answer: 68 + 29 ≈ 70 + 30 = 100; Adjust: 68 + 29 = (70 - 2) + (30 - 0) = 70 + 30 - 2 = 98

Question 9: Add 57 + 46 using mental strategies of splitting and combining.

Answer: 57 + 46 = (50 + 7) + (40 + 6) = (50 + 40) + (7 + 6) = 90 + 13 = 103

Question 10: Challenge: Find the sum of 89 + 76 using mental strategies, explaining your steps.

Answer: Add 89 + 76 by rounding 76 to 80: 89 + 80 = 169, then subtract 4 (since 80 was 4 too many). 169 - 4 = 165.

Question 11: Identify the common mistake: Calculating 45 + 37 as 80. What's wrong and how to correct it?

Answer: Incorrect: 45 + 37 = 80; Correct method: 45 + 30 = 75, plus 7 = 82.