Numbers from 100 to 999 that include hundreds, tens, and ones places. Each digit represents its place value: 345 = 300 + 40 + 5.
Recognizing that each digit's position determines its value. Hundreds place, tens place, and ones place form the foundation for working with numbers up to 1000.
When adding, if any place value (ones, tens) totals 10 or more, carry to the next higher place. Example: 247 + 186 requires regrouping in both ones and tens.
When subtracting, if a digit in the minuend is smaller than the corresponding digit in the subtrahend, borrow from the next higher place. Example: 523 - 187 requires borrowing.
Represents groups of 100
Example: 345 ā 3 Ć 100 = 300
Represents groups of 10
Example: 345 ā 4 Ć 10 = 40
Represents individual units
Example: 345 ā 5 Ć 1 = 5
- Add ones place first
- Carry if sum ā„ 10
- Add tens place (including carried)
- Carry if sum ā„ 10
- Add hundreds place (including carried)
- Subtract ones place first
- Borrow if top < bottom
- Subtract tens place (including borrowed)
- Borrow if top < bottom
- Subtract hundreds place (including borrowed)
- Read: Carefully read the entire problem
- Identify: Find numbers and clue words
- Plan: Decide operation and strategy
- Solve: Perform calculation with place value
- Check: Verify answer makes sense
- Use base-10 blocks: Visualize hundreds, tens, and ones
- Line up digits: Align numbers by place value when calculating
- Check reasonableness: Estimate first to verify your answer
- Start with zeros: Practice with numbers ending in zero first
- Break it down: Add/subtract place values separately
⢠Forgetting to regroup when necessary
⢠Misaligning digits by place value
⢠Making calculation errors with larger numbers
⢠Not checking if the answer is reasonable
⢠Confusing place value positions
Context: Book sales across two days
Given: 247 books on Monday + 186 books on Tuesday
Question: Total number of books sold
Operation: Addition (keyword: "total")
Strategy: Adding with regrouping in ones and tens places
- Set up equation: 247 + 186 = ?
- Add ones place: 7 + 6 = 13 ā Write 3, carry 1
- Add tens place: 4 + 8 + 1 (carried) = 13 ā Write 3, carry 1
- Add hundreds place: 2 + 1 + 1 (carried) = 4
- Combine results: 433 total books
"Total books" means we need to add both amounts together
Monday books + Tuesday books = Total books
247 + 186 = ?
Ones: 7 + 6 = 13 ā Write 3, carry 1
Tens: 4 + 8 + 1 = 13 ā Write 3, carry 1
Hundreds: 2 + 1 + 1 = 4
Answer: 433
The bookstore sold 433 books in total
The bookstore sold 433 books in total
⢠Regrouping: When place value exceeds 9, carry to next place
⢠Place Value: Keep hundreds, tens, and ones separate during addition
⢠Sequential Processing: Add from right to left
Context: Books being donated away
Given: Started with 523 books, donated 187
Question: How many remain?
Operation: Subtraction (keyword: "left")
Strategy: Borrowing needed in ones and tens places
"Left" means we need to subtract because some were donated away
Total books - Donated books = Remaining books
523 - 187 = ?
Ones: 3 < 7, so borrow ā 13 - 7 = 6
Tens: 1 < 8 (after borrowing), so borrow ā 11 - 8 = 3
Hundreds: 4 - 1 = 3
Answer: 336
The library has 336 books left
The library has 336 books left
⢠Borrowing: When top number is smaller, borrow from next place
⢠Place Value: Maintain value during borrowing across all places
⢠Change Situation: Something was taken away
Context: School enrollment across three grades
Given: 245 + 178 + 193 students in different grades
Question: Total number of students
Operation: Multiple additions with regrouping
All grades need to be added together to find the total
245 + 178 = 423 students (Grades 1 and 2)
423 + 193 = 616 students total
The school has 616 students altogether
The school has 616 students altogether
⢠Multi-step Problems: Add one pair at a time
⢠Sequential Addition: Combine totals step by step
⢠Grouping Strategy: Organize different categories
Context: Comparing two collections
Given: Tom: 634 cards, Sister: 287 cards
Question: Difference between their collections
Operation: Subtraction (keyword: "more")
Strategy: Find the difference between two three-digit amounts
"How many more" means we find the difference between the two amounts
Tom's collection - Sister's collection = Difference
634 - 287 = ?
Ones: 4 < 7, so borrow ā 14 - 7 = 7
Tens: 2 < 8 (after borrowing), so borrow ā 12 - 8 = 4
Hundreds: 5 - 2 = 3
Answer: 347
Tom collected 347 more cards than his sister
Tom collected 347 more cards than his sister
⢠Comparison Problems: Subtract to find the difference
⢠Borrowing: Needed when subtracting larger digit from smaller
⢠Comparison Keywords: "more than," "less than," "difference"
Context: Box inventory changes throughout the day
Given: Started with 752, shipped 268, received 195
Question: Final number of boxes
Operations: Subtraction first, then addition (both with regrouping)
First subtract shipped boxes, then add new delivery
752 - 268 = 484 boxes remaining after morning
484 + 195 = 679 boxes total
The warehouse has 679 boxes now
The warehouse has 679 boxes now
⢠Sequential Operations: Perform operations in order given
⢠Time Sequence: Follow chronological order of events
⢠Multiple Operations: Handle one at a time with proper regrouping
ABC + DEF = Result
ABC - DEF = Result
ABC = AĆ100 + BĆ10 + CĆ1
ADD FROM RIGHT TO LEFT, CARRY WHEN NEEDED!
SUBTRACT FROM RIGHT TO LEFT, BORROW WHEN NEEDED!
ALWAYS ALIGN BY PLACE VALUE!
⢠Check each place value before starting to anticipate regrouping needs
⢠Use expanded form to understand place value relationships
⢠Practice with base-10 blocks to visualize regrouping
⢠Estimate first to have a target answer range
⢠Always verify your answer makes sense in context