Decoration for Festival · Learner pages

Lesson 1 · Add tens and ones

Add two two-digit numbers without regrouping.

Name or initials: ____________   Date: ____________

A ten is ten ones. Align tens with tens and ones with ones.

1. Split each number. 24 is 20 + 4. 13 is 10 + 3.
2. Add the tens. 20 + 10 = 30.
3. Add the ones. 4 + 3 = 7.
4. Join the parts. 30 + 7 = 37, so 24 + 13 = 37.

Worked example: 32 + 25 = (30 + 20) + (2 + 5) = 50 + 7 = 57. Check: adding 25 must make 32 larger.

1. What is 23 + 14?

   1. 37 · 2. 27 · 3. 41

2. In 46, the 4 means…

   1. 4 ones · 2. 4 tens · 3. 40 tens

3. What is 51 + 28?

   1. 69 · 2. 89 · 3. 79

Discuss: Make an addition story about 21 red paper flags and 16 blue flags. Find the total.

Lesson 2 · Regroup ten ones

Exchange ten ones for one ten when adding.

Name or initials: ____________   Date: ____________

Ten loose ones can be grouped as one ten without changing the total.

1. Add the parts. For 27 + 15, add 20 + 10 = 30 and 7 + 5 = 12.
2. Find ten in the ones. Twelve ones can be separated into ten ones and two ones.
3. Make a new ten. Exchange ten ones for one ten. Now there are 4 tens and 2 ones.
4. Write and check. 40 + 2 = 42. Check by making ten: 27 + 3 + 12 = 42.

Worked example: 36 + 18: 30 + 10 = 40; 6 + 8 = 14. Exchange ten of those ones. We have 50 + 4 = 54.

1. What is 28 + 15?

   1. 33 · 2. 43 · 3. 413

2. Ten ones can be exchanged for…

   1. 10 tens · 2. 2 tens · 3. 1 ten

3. What is 47 + 16?

   1. 63 · 2. 53 · 3. 613

Discuss: Explain with a drawing why 28 + 14 gives 42, not 312.

Lesson 3 · Exchange a ten to subtract

Subtract a two-digit number and check by addition.

Name or initials: ____________   Date: ____________

Subtraction finds what remains or the difference. Exchange a ten when there are too few loose ones.

1. Look at the ones. For 42 - 17, two loose ones are not enough to remove seven.
2. Exchange one ten. 42 is 4 tens and 2 ones. Exchange one ten to make 3 tens and 12 ones.
3. Subtract each part. 12 ones - 7 ones = 5 ones. 3 tens - 1 ten = 2 tens.
4. Check the result. The answer is 25. Check: 25 + 17 = 42.

Worked example: 53 - 26: exchange one ten to show 4 tens and 13 ones. 13 - 6 = 7 and 4 tens - 2 tens = 2 tens. Answer 27. Check 27 + 26 = 53.

1. What is 41 - 16?

   1. 35 · 2. 23 · 3. 25

2. Which check proves 52 - 28 = 24?

   1. 24 + 28 = 52 · 2. 52 + 24 = 28 · 3. 28 - 24 = 52

3. What is 64 - 32?

   1. 42 · 2. 32 · 3. 36

Discuss: A group makes 61 paper flowers and uses 24. Show how to find and check how many remain.

Final check · Set 1

Try one set after the lessons. Use the other set after reviewing any errors.

1. What is 34 + 22?

   56 / 46 / 66

2. What is 42 + 17?

   49 / 59 / 69

3. What is 26 + 18?

   34 / 414 / 44

4. What is 38 + 24?

   62 / 52 / 612

5. What is 51 - 27?

   34 / 24 / 26

6. How can you check 63 - 18 = 45?

   63 + 18 = 45 / 45 - 18 = 63 / 45 + 18 = 63

Final check · Set 2

Try one set after the lessons. Use the other set after reviewing any errors.

1. What is 25 + 32?

   47 / 57 / 67

2. What is 16 + 43?

   49 / 69 / 59

3. What is 29 + 14?

   43 / 33 / 413

4. What is 45 + 27?

   62 / 72 / 712

5. What is 62 - 35?

   37 / 33 / 27

6. What is 73 - 21?

   52 / 42 / 54