Question 1: Subtract 45 from 78 using mental strategies. Show your process.

Answer: 33

Question 2: Calculate 62 - 29 mentally. Explain your strategy.

Answer: 33

Question 3: Use compatible numbers to mentally find 73 - 48.

Answer: 25

Question 4: Subtract 57 from 92 by decomposing the numbers. Show your working.

Answer: 92 - 57 = (92 - 50) - 7 = 42 - 7 = 35

Question 5: A basket has 86 apples. After selling 29, how many are left? Use mental subtraction to find out.

Answer: 57

Question 6: Subtract 33 from 60 using a mental strategy you prefer. Describe your method.

Answer: 60 - 33 = 60 - 30 - 3 = 27

Question 7: Compute 85 - 69 mentally. Explain your reasoning.

Answer: 16

Question 8: Solve 94 - 47 in your head. Use compatible numbers in your explanation.

Answer: 94 - 50 + 3 = 44

Question 9: A train travels 68 miles. It then travels an additional 23 miles. How many miles has it traveled in total? Use mental addition and subtraction to find the total distance traveled in a different way.

Answer: 91

Question 10: Estimate 88 - 49 using rounding, then check your estimate with exact mental subtraction.

Answer: 88 - 50 = 38; exact: 39

Question 11: Identify the mistake in this mental subtraction: 74 - 59 = 15. Correct the error.

Answer: The calculation is incorrect because 74 - 59 = 15 is wrong; actual difference is 15, but the process may have misused mental strategies. Correct process: 70 - 60 = 10, then add 1 to compensate = 11.

Question 12: Challenge: Find 97 - 58 mentally by breaking down the numbers into hundreds, tens, and ones. Show your detailed working.

Answer: 97 - 58 = (100 - 50) + (0 - 8) = 50 + (-8) = 42