34 + 25
Place value addition: Adding numbers by breaking them into tens and ones, then combining like place values
- Break each number into tens and ones
- Add the tens together
- Add the ones together
- Combine the results
34 = 30 + 4 (3 tens and 4 ones)
25 = 20 + 5 (2 tens and 5 ones)
30 + 20 = 50
4 + 5 = 9
50 + 9 = 59
34 + 25 = 59
• Place value: Separate tens and ones to make addition easier
• Like place values: Only add tens to tens and ones to ones
• Combining: Add the final tens and ones together
34 → 3 tens
25 → 2 tens
Total: 3 + 2 = 5 tens = 50
34 → 4 ones
25 → 5 ones
Total: 4 + 5 = 9 ones
50 + 9 = 59
Or: 5 tens + 9 ones = 59
47 + 38
Regrouping: Converting 10 or more ones into a new ten when adding
47 = 40 + 7 (4 tens and 7 ones)
38 = 30 + 8 (3 tens and 8 ones)
40 + 30 = 70
7 + 8 = 15 ones
Since 15 ≥ 10, we need to regroup!
15 ones = 1 ten + 5 ones
Add this extra ten to our tens: 70 + 10 = 80
80 + 5 = 85
47 + 38 = 85
• Regrouping: When ones add to 10 or more, convert to tens
• Place value: Separate tens and ones for easier calculation
• Combining: Add final tens and ones together
47 → 4 tens + 7 ones
38 → 3 tens + 8 ones
7 ones + 8 ones = 15 ones
15 ones = 1 ten + 5 ones
Tens: 4 + 3 + 1 = 8 tens
Ones: 5 ones
Answer: 85
60 + 20
Adding multiples of 10: Adding numbers that only have tens place values (no ones)
60 = 6 tens + 0 ones
20 = 2 tens + 0 ones
6 tens + 2 tens = 8 tens
0 ones + 0 ones = 0 ones
8 tens + 0 ones = 80
60 + 20 = 80
• Place value: Understand that multiples of 10 only have tens place
• Like place values: Only add tens to tens and ones to ones
• Zero ones: When adding multiples of 10, the ones place remains zero
60 → 6 tens
20 → 2 tens
Total: 6 + 2 = 8 tens = 80
60 → 0 ones
20 → 0 ones
Total: 0 + 0 = 0 ones
8 tens + 0 ones = 80
Place value: The value of a digit based on its position in a number
Tens place: The second digit from the right, representing groups of ten
Ones place: The rightmost digit, representing individual units
Regrouping: Converting 10 or more ones into a new ten when adding
Expanded form: Writing a number as the sum of its place values (e.g., 45 = 40 + 5)
- Recognize the numbers: Look at each number and identify tens and ones
- Break apart numbers: Write each number in expanded form (tens + ones)
- Add tens with tens: Combine all the tens together
- Add ones with ones: Combine all the ones together
- Check for regrouping: If ones total is 10 or more, convert to tens
- Combine results: Add the final tens and ones together
• Place value formula: Two-digit number AB = A×10 + B
• Addition rule: (T₁ + O₁) + (T₂ + O₂) = (T₁ + T₂) + (O₁ + O₂)
• Regrouping rule: When O₁ + O₂ ≥ 10, convert to tens and ones
• Like place values: Only add tens to tens and ones to ones
23 + 14 = (20 + 3) + (10 + 4) = (20 + 10) + (3 + 4) = 30 + 7 = 37
38 + 27 = (30 + 8) + (20 + 7) = (30 + 20) + (8 + 7) = 50 + 15 = 50 + 10 + 5 = 65
40 + 30 = (4 tens) + (3 tens) = 7 tens = 70
Word problems: Real-life situations requiring mathematical operations using place value strategies
Emma has 36 red marbles
Emma has 47 blue marbles
This is an addition problem: 36 + 47
36 = 30 + 6 (3 tens and 6 ones)
47 = 40 + 7 (4 tens and 7 ones)
Tens: 30 + 40 = 70
Ones: 6 + 7 = 13
13 ones = 1 ten + 3 ones
Add this extra ten to our tens: 70 + 10 = 80
80 + 3 = 83
Emma has 83 marbles altogether.
Emma has 83 marbles altogether.
• Problem solving: Identify operation needed from context
• Place value: Break numbers into tens and ones
• Regrouping: When ones add to 10 or more, convert to tens
Red marbles: 36
Blue marbles: 47
Operation: Addition
36 = 30 + 6
47 = 40 + 7
Tens: 30 + 40 = 70
Ones: 6 + 7 = 13
Regroup: 13 = 1 ten + 3 ones
Total: 70 + 10 + 3 = 83
Multi-step problems: Problems requiring multiple addition operations solved sequentially using place value strategies
Fiction books: 45
Non-fiction books: 38
Total initially: 45 + 38
45 = 40 + 5, 38 = 30 + 8
Tens: 40 + 30 = 70
Ones: 5 + 8 = 13
Since 13 ≥ 10, regroup: 13 = 1 ten + 3 ones
70 + 10 = 80, plus 3 ones = 83 books initially
Now add the 29 new books: 83 + 29
83 = 80 + 3, 29 = 20 + 9
Tens: 80 + 20 = 100
Ones: 3 + 9 = 12
Since 12 ≥ 10, regroup: 12 = 1 ten + 2 ones
100 + 10 = 110, plus 2 ones = 112 books total
The library has 112 books now.
The library has 112 books.
• Order of operations: Work from left to right for addition
• Place value: Break each number into tens and ones
• Regrouping: Apply when necessary in each operation
Fiction: 45 books
Non-fiction: 38 books
Total: 45 + 38
45 + 38
45 = 40 + 5
38 = 30 + 8
Ones: 5 + 8 = 13 (regroup)
Result: 83 books
83 + 29
83 = 80 + 3
29 = 20 + 9
Ones: 3 + 9 = 12 (regroup)
Result: 112 books