Review Addition and Subtraction Worksheets for 3rd Grade

Master addition and subtraction operations: regrouping, place value, word problems, and estimation techniques through these 3 detailed exercises.

Solution: Exercises 1 to 3
1 Addition with Regrouping
Exercise 1
Solve:
247 + 186 = ?
Definition:

Addition: Combining two or more numbers to find their total sum. When adding larger numbers, we add by place value (ones, tens, hundreds).

Addition method:
  1. Line up numbers by place value (ones under ones, tens under tens)
  2. Add digits in each place value column starting from the right
  3. If the sum in any column is 10 or more, carry over to the next column
Setup
247
+ 186
Addition
433
Step 1: Add ones column

7 + 6 = 13 → Write 3, carry 1

Step 2: Add tens column

4 + 8 + 1 (carried) = 13 → Write 3, carry 1

Step 3: Add hundreds column

2 + 1 + 1 (carried) = 4 → Write 4

247 + 186 = 433
Final answer:

247 + 186 = 433

Applied rules:

• Place Value: Align numbers by place value before adding

• Carrying: When sum ≥ 10, carry the tens digit to the next column

• Regrouping: Breaking numbers into groups of 10 to simplify addition

2 Subtraction with Borrowing
Exercise 2
Solve:
523 - 178 = ?
Definition:

Subtraction: Finding the difference between two numbers. When subtracting larger digits from smaller digits, we borrow from the next higher place value.

Setup
523
- 178
Subtraction
345
Step 1: Subtract ones column

3 - 8 → Not possible, so borrow 1 ten (13 - 8 = 5)

Step 2: Subtract tens column

1 - 7 → Not possible, so borrow 1 hundred (11 - 7 = 4)

Step 3: Subtract hundreds column

4 - 1 = 3

523 - 178 = 345
Final answer:

523 - 178 = 345

Applied rules:

• Borrowing: When the top digit is smaller than the bottom digit, borrow from the next higher place value

• Place Value: Always subtract digits in the same place value column

• Regrouping: Breaking a higher place value unit into 10 units of the next lower place value

3 Word Problem
Exercise 3
Sarah has 345 stickers. She gives 128 stickers to her friend. Then she buys 87 more stickers. How many stickers does Sarah have now?
Definition:

Word Problems: Real-life situations that require mathematical operations to solve. We identify key information and determine which operations to use.

Initial amount
345
Subtract given away
345 - 128
Add new stickers
+ 87
Step 1: Identify operations needed

Start with 345, subtract 128 (given away), then add 87 (new stickers)

Step 2: Calculate 345 - 128

345 - 128 = 217

Step 3: Calculate 217 + 87

217 + 87 = 304

Step 4: Final calculation

345 - 128 + 87 = 304

Sarah has 304 stickers now
Final answer:

Sarah has 304 stickers now

Applied rules:

• Problem Solving: Read carefully, identify key information, determine operations

• Order of Operations: Work left to right when only addition and subtraction

• Verification: Check that the answer makes sense in the context of the problem

Key Concepts and Methods
A + B = C
Addition Formula
Addition
A + B = C
Combining numbers
Subtraction
A - B = C
Finding difference
Regrouping
10 ones = 1 ten
Borrowing/carrying
Key definitions:

Addition: Combining two or more numbers to get a sum

Subtraction: Finding the difference between two numbers

Place Value: The value of a digit based on its position (ones, tens, hundreds)

Addition Method:
  1. Align numbers by place value
  2. Add from right to left (ones, tens, hundreds)
  3. Carry over if sum ≥ 10
Subtraction Method:
  1. Align numbers by place value
  2. Subtract from right to left
  3. Borrow if top digit is smaller
Tip 1: Always check your work by doing the opposite operation (addition check: 433 - 186 = 247)
Tip 2: Use base-10 blocks or drawings to visualize regrouping when learning
Tip 3: Estimate first to check if your answer is reasonable
Common errors: Forgetting to carry/borrow, misaligning numbers by place value, calculation mistakes in basic facts.
Estimation: Round numbers to nearest 10 or 100 to estimate sums/differences before calculating exact answers.
Review: Place Value and Estimation
100s + 10s + 1s
Place Value System
Place Value:

Ones place: Rightmost digit (value × 1)

Tens place: Second from right (value × 10)

Hundreds place: Third from right (value × 100)

Estimation Method:
  1. Round each number to the nearest 10 or 100
  2. Perform the operation with rounded numbers
  3. Compare to exact answer to check reasonableness
Estimation Example: 247 + 186 ≈ 250 + 190 = 440 (close to actual 433)
Checking Addition: Switch order of addends - 247 + 186 = 186 + 247
Checking Subtraction: Add the result to the subtracted number - 345 - 178 = 167, then 167 + 178 = 345
Regrouping: When adding, 10 ones become 1 ten. When subtracting, 1 ten becomes 10 ones.
Word Problem Strategy: Read carefully, identify numbers and operations, solve step by step.
Key Rules to Remember:

• Alignment: Always line up numbers by place value

• Carrying: When sum ≥ 10 in any column, carry to the next column

• Borrowing: When top digit is smaller, borrow from next higher place value

• Checking: Verify answers using inverse operations

• Estimation: Use to check if answers are reasonable

Addition and Subtraction Properties and Strategies
A + B = B + A
Commutative Property
Key definitions:

Commutative Property: Order doesn't matter in addition (A + B = B + A)

Associative Property: Grouping doesn't matter in addition ((A + B) + C = A + (B + C))

Identity Property: Adding zero doesn't change the number (A + 0 = A)

Mental Math Strategies:
  1. Counting On: Start with the larger number and count up
  2. Make Tens: Break apart numbers to make multiples of 10
  3. Compensation: Adjust one number to make the calculation easier
Tip 1: To add 9, add 10 and subtract 1 (e.g., 247 + 9 = 247 + 10 - 1 = 256)
Tip 2: To subtract 9, subtract 10 and add 1 (e.g., 523 - 9 = 523 - 10 + 1 = 514)
Tip 3: Look for doubles (e.g., 25 + 25 = 50) to make mental math faster
Tip 4: Use fact families (e.g., if 247 + 186 = 433, then 433 - 247 = 186)
Subtraction Facts: Remember that subtraction is the inverse of addition.
Regrouping Visualization: Think of exchanging bills - 1 hundred = 10 tens.
Important Patterns:

• Addition Pattern: Adding increases the total

• Subtraction Pattern: Subtracting decreases the total

• Zero Pattern: Adding or subtracting zero doesn't change the number

• Same Numbers: A - A = 0

Questions & Answers

Question: My students often forget to carry over when adding or borrow when subtracting. What strategies help them remember?

Answer: Great question! Here are effective strategies to help students remember carrying and borrowing:

  • Visual Markers: Have students write the carried number in a different color or circle it to make it stand out
  • Physical Actions: Teach them to physically touch the carried number and say "plus" when adding it to the next column
  • Memory Device: "More than 9? Carry next door!" for addition and "Need more? Go next door and borrow!" for subtraction
  • Base-10 Blocks: Use manipulatives to physically show regrouping before transitioning to paper

Practice with smaller numbers first, then gradually increase complexity. Consistent practice with immediate feedback helps build the habit of checking for carries and borrows.

Question: How can I help my child understand when to use addition versus subtraction in word problems?

Answer: Word problems can be tricky! Here's a strategy to help identify operations:

  • Addition Keywords: altogether, combined, total, sum, in all, increased by, more than
  • Subtraction Keywords: difference, fewer, less than, decreased by, take away, left, remaining
  • Visual Representation: Draw pictures or use objects to model the situation
  • Context Clues: Ask "Are we putting things together?" (addition) or "Are we taking some away?" (subtraction)

For example, "Sarah has 345 stickers and gives away 128" → giving away means subtracting. Practice identifying keywords and drawing models to reinforce understanding.

Question: Sometimes when I subtract, I get confused about borrowing. How do I know when to borrow?

Answer: You need to borrow in subtraction when the top digit is smaller than the bottom digit in any column. Here's how to think about it:

  • Check Each Column: Starting from the right, compare top and bottom digits
  • When Top is Smaller: If top digit < bottom digit, you must borrow
  • How to Borrow: Take 1 from the next higher place value (which reduces it by 1) and add 10 to the current column
  • Example: In 523 - 178, in the ones column: 3 < 8, so borrow 1 ten to make it 13 - 8 = 5

Think of borrowing like exchanging money: if you have 1 ten-dollar bill and need to pay 8 dollars, you exchange the 10 for 10 one-dollar bills, giving you 13 dollars to pay with.