GRADE 2 · A4 PRINT VIEW
Decoration for Festival · Answer guide
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Lesson 1 · Add tens and ones
Add two two-digit numbers without regrouping.
What is 23 + 14?
Answer: 37. 20 + 10 = 30 and 3 + 4 = 7, so the sum is 37.
In 46, the 4 means…
Answer: 4 tens. The tens digit is 4, so it represents 40.
What is 51 + 28?
Answer: 79. 50 + 20 = 70 and 1 + 8 = 9; total 79.
Discuss: Make an addition story about 21 red paper flags and 16 blue flags. Find the total.
Teaching note: Do not add a tens digit to a ones digit. They name different-sized groups. Open responses need discussion; they are not automatically marked.
Lesson 2 · Regroup ten ones
Exchange ten ones for one ten when adding.
What is 28 + 15?
Answer: 43. 20 + 10 = 30 and 8 + 5 = 13. 30 + 13 = 43.
Ten ones can be exchanged for…
Answer: 1 ten. One ten has exactly the same value as ten ones.
What is 47 + 16?
Answer: 63. 40 + 10 = 50 and 7 + 6 = 13. 50 + 13 = 63.
Discuss: Explain with a drawing why 28 + 14 gives 42, not 312.
Teaching note: Regrouping does not create extra objects. Ten ones and one ten are the same amount. Open responses need discussion; they are not automatically marked.
Lesson 3 · Exchange a ten to subtract
Subtract a two-digit number and check by addition.
What is 41 - 16?
Answer: 25. Exchange 41 as 3 tens and 11 ones. 11 - 6 = 5; 3 tens - 1 ten = 2 tens.
Which check proves 52 - 28 = 24?
Answer: 24 + 28 = 52. The amount removed plus the amount left gives the starting amount.
What is 64 - 32?
Answer: 32. 6 tens - 3 tens = 3 tens; 4 ones - 2 ones = 2 ones.
Discuss: A group makes 61 paper flowers and uses 24. Show how to find and check how many remain.
Teaching note: You cannot swap the subtraction just to make it easy: 2 - 7 is not 7 - 2. Regroup the whole number instead. Open responses need discussion; they are not automatically marked.
Final check · Set 1
Try one set after the lessons. Use the other set after reviewing any errors.
What is 34 + 22?
56. 30 + 20 = 50; 4 + 2 = 6; total 56.
What is 42 + 17?
59. 40 + 10 = 50 and 2 + 7 = 9.
What is 26 + 18?
44. 20 + 10 + 6 + 8 = 30 + 14 = 44.
What is 38 + 24?
62. 30 + 20 = 50; 8 + 4 = 12; 50 + 12 = 62.
What is 51 - 27?
24. 51 = 40 + 11; subtract 20 + 7 to get 20 + 4 = 24.
How can you check 63 - 18 = 45?
45 + 18 = 63. Adding the removed amount back should restore 63.
Final check · Set 2
Try one set after the lessons. Use the other set after reviewing any errors.
What is 25 + 32?
57. 20 + 30 = 50 and 5 + 2 = 7.
What is 16 + 43?
59. 10 + 40 = 50 and 6 + 3 = 9.
What is 29 + 14?
43. 20 + 10 + 9 + 4 = 30 + 13 = 43.
What is 45 + 27?
72. 40 + 20 = 60 and 5 + 7 = 12; total 72.
What is 62 - 35?
27. 62 = 50 + 12; remove 30 + 5 to leave 20 + 7.
What is 73 - 21?
52. 70 - 20 = 50 and 3 - 1 = 2.
Original chapter companion covering two-digit addition and subtraction using place value and regrouping. It does not reproduce or solve every textbook exercise. An adult should read prompts aloud and support handling small objects safely.