Key Concepts & Definitions
Example: 23 + 15 = 38
Properties: Commutative (a+b=b+a), Associative ((a+b)+c=a+(b+c))
Example: 45 - 18 = 27
Key Point: Subtraction is the inverse of addition.
Example: 4 × 3 = 4+4+4 = 12
Properties: Commutative (a×b=b×a), Associative ((a×b)×c=a×(b×c))
Example: 12 ÷ 3 = 4 (12 split into 3 equal groups of 4)
Key Point: Division is the inverse of multiplication.
- Read: Understand what the problem is asking
- Plan: Decide which operation(s) to use
- Solve: Work through the calculation
- Check: Verify your answer makes sense
Multi-digit addition: Adding numbers with multiple digits by aligning place values and carrying when necessary.
- Align numbers by place value (ones under ones, tens under tens)
- Add from right to left (ones, then tens, then hundreds)
- Carry over when sum exceeds 9
- Write the final sum
247
+ 186
-----
7 + 6 = 13, write 3, carry 1
4 + 8 + 1 (carry) = 13, write 3, carry 1
2 + 1 + 1 (carry) = 4
247 + 186 = 433
• Place value alignment: Always align digits by their place value
• Carrying: When sum ≥ 10, carry the extra digit to the next column
• Right-to-left: Add columns starting from the rightmost
Multi-digit subtraction: Subtracting numbers with multiple digits by aligning place values and borrowing when necessary.
523
- 178
-----
3 < 8, so borrow 1 from tens: 13 - 8 = 5
After borrowing: 1 < 7, so borrow 1 from hundreds: 11 - 7 = 4
After borrowing: 4 - 1 = 3
523 - 178 = 345
• Borrowing: When top digit < bottom digit, borrow from next higher place
• Place value: Always subtract digits in the same place value
• Check work: Add the difference back to the subtrahend to verify
Multiplication: Repeated addition of equal groups. 7 × 8 means 7 groups of 8, or 8 groups of 7.
7 × 8 = 8 + 8 + 8 + 8 + 8 + 8 + 8 = 56
7 × 7 = 49, so 7 × 8 = 49 + 7 = 56
8 × 7 = 56 (commutative property)
7 × 8 = 56
• Commutative property: Order doesn't matter (7 × 8 = 8 × 7)
• Memorization: Knowing multiplication tables helps solve quickly
• Repeated addition: Multiplication is shortcut for adding equal groups
Division with remainder: Dividing a number that doesn't divide evenly, leaving some left over.
4 × 1 = 4, 4 × 2 = 8, 4 × 3 = 12, 4 × 4 = 16, 4 × 5 = 20, 4 × 6 = 24
4 × 6 = 24, which is the largest multiple of 4 that is ≤ 25
25 - 24 = 1 remainder
25 ÷ 4 = 6 remainder 1
25 ÷ 4 = 6 remainder 1
• Division relationship: Dividend = Divisor × Quotient + Remainder
• Remainder check: Remainder must be less than divisor
• Multiplication facts: Knowing multiplication helps with division
Word problems: Real-life situations that require mathematical operations to solve.
Total stickers = 48, Number of friends = 6, Need to find: stickers per friend
"Share equally" means division: 48 ÷ 6
48 ÷ 6 = 8 (since 6 × 8 = 48)
Each friend gets 8 stickers
Each friend will get 8 stickers.
• Problem analysis: Identify what's given and what's needed
• Operation selection: Choose the right operation for the situation
• Context verification: Make sure answer makes sense in context
Place Value: Understanding hundreds, tens, and ones places
Operations: Addition, subtraction, multiplication, and division
Word Problems: Translating real-world scenarios into math
Geometry: Identifying shapes and their properties
Fractions: Understanding parts of a whole
- Read carefully: Take time to understand each question
- Check work: Always verify calculations when possible
- Use scratch paper: Show your work for complex problems
- Manage time: Don't spend too long on one question
• Addition: a + b = sum
• Subtraction: minuend - subtrahend = difference
• Multiplication: a × b = product
• Division: dividend ÷ divisor = quotient (with possible remainder)
• Place value: 10 ones = 1 ten, 10 tens = 1 hundred