Question 1: Subtract 47 from 85 using mental strategies. Show your working.

Answer: 38

Question 2: Estimate 63 - 29 mentally by rounding to the nearest ten, then find the exact difference.

Answer: 34

Question 3: A student subtracts 58 from 93 and gets 45. Identify the common mistake and correct it.

Answer: Misreading the subtraction or incorrectly borrowing, correct answer is 35.

Question 4: Calculate 72 - 46 mentally, using compatible numbers or other strategies. Show your steps.

Answer: 26

Question 5: Explain why subtracting 59 from 80 might be easier than subtracting 59 from 81 mentally.

Answer: Because 80 is closer to 59, making the subtraction simpler and quicker.

Question 6: A student subtracts 68 from 104 by breaking 68 into 60 and 8, then subtracting each part separately. Is this correct? Why or why not?

Answer: Yes, using decomposition helps mental subtraction; total difference is 36.

Question 7: Subtract 59 from 100. Use a mental strategy to find the answer and explain your method.

Answer: 41; by subtracting 60 and then adding 1 back, or subtracting 50 then 9.

Question 8: A student incorrectly subtracts 43 from 76 and gets 33. Find the mistake and correct the answer.

Answer: Incorrect borrowing or subtraction; correct answer is 33, but check calculations for errors.

Question 9: Using mental strategies, subtract 56 from 89 by decomposing numbers. Show your working.

Answer: 33; subtract 50 and 6 separately, then combine.

Question 10: Challenge: Subtract 94 from 150 mentally by breaking numbers into hundreds and tens. Explain your process.

Answer: Subtract 100 from 150 to get 50, then subtract 4 from 50 to get 46.

Question 11: A student claims subtracting 65 from 100 is always easier if they round 100 to 100. Is this true? Why or why not?

Answer: False; sometimes exact subtraction is easier, especially when rounding changes the number significantly.