Fractions - Seventh Grade
Complete Notes & Formulas
1. Understanding Fractions
What is a Fraction?
numerator/denominator
Numerator: Top number (parts you have)
Denominator: Bottom number (total parts)
Types of Fractions
Type | Definition | Example |
---|---|---|
Proper Fraction | Numerator < Denominator | 3/4, 2/5, 7/8 |
Improper Fraction | Numerator ≥ Denominator | 7/4, 9/5, 11/3 |
Mixed Number | Whole number + Proper fraction | 2 1/3, 5 2/7 |
2. Equivalent Fractions
Definition
Equivalent fractions have DIFFERENT numerators
and denominators but represent the SAME VALUE
Example: 1/2 = 2/4 = 3/6 = 4/8
Method 1: Multiply by Same Number
a/b × n/n = a×n/b×n
Multiply both numerator and denominator by the SAME number
Example: Find equivalent fractions of 2/3
Multiply by 2: 2/3 × 2/2 = 4/6
Multiply by 3: 2/3 × 3/3 = 6/9
Multiply by 4: 2/3 × 4/4 = 8/12
Answer: 2/3 = 4/6 = 6/9 = 8/12
Method 2: Divide by Same Number
Divide both numerator and denominator by a COMMON FACTOR
This simplifies the fraction
3. Simplifying Fractions to Lowest Terms
What is Lowest Terms?
A fraction is in LOWEST TERMS when the
numerator and denominator have NO common factors
other than 1 (they are relatively prime)
Formula
a/b ÷ GCF/GCF = a÷GCF/b÷GCF
Divide both by the Greatest Common Factor (GCF)
Steps to Simplify
Step 1: Find the GCF of numerator and denominator
Step 2: Divide both numerator and denominator by GCF
Step 3: The result is the simplified fraction
Example: Simplify 24/36
Step 1: Find GCF(24, 36)
Factors of 24: 1, 2, 3, 4, 6, 8, 12, 24
Factors of 36: 1, 2, 3, 4, 6, 9, 12, 18, 36
GCF = 12
Step 2: Divide both by 12
24 ÷ 12 = 2
36 ÷ 12 = 3
Answer: 24/36 = 2/3
4. Least Common Denominator (LCD)
What is LCD?
LCD is the SMALLEST common denominator
for a set of fractions
• It's the LCM (Least Common Multiple) of denominators
• Needed for adding and subtracting fractions
How to Find LCD
Step 1: List multiples of each denominator
Step 2: Find the smallest common multiple
Step 3: That's your LCD!
Example: Find LCD of 1/4 and 1/6
Multiples of 4: 4, 8, 12, 16, 20, 24...
Multiples of 6: 6, 12, 18, 24, 30...
Smallest common multiple: 12
Convert to LCD:
1/4 = 3/12 (multiply by 3/3)
1/6 = 2/12 (multiply by 2/2)
Answer: LCD = 12
5. Comparing and Ordering Fractions
Method 1: Same Denominator
If denominators are SAME:
Compare the NUMERATORS
Larger numerator = Larger fraction
Example: 5/8 > 3/8 (because 5 > 3)
Method 2: Same Numerator
If numerators are SAME:
Compare the DENOMINATORS
Smaller denominator = Larger fraction
Example: 2/3 > 2/5 (because 3 < 5)
Method 3: Different Numerators and Denominators
Step 1: Find the LCD of both fractions
Step 2: Convert both fractions to LCD
Step 3: Compare numerators
Example: Compare 2/3 and 3/4
Step 1: LCD of 3 and 4 is 12
Step 2: Convert to LCD
2/3 = 8/12 (multiply by 4/4)
3/4 = 9/12 (multiply by 3/3)
Step 3: Compare: 8/12 < 9/12
Answer: 2/3 < 3/4
6. Converting Between Mixed Numbers and Improper Fractions
Mixed Number to Improper Fraction
ab/c = (a×c)+b/c
Step 1: Multiply whole number × denominator
Step 2: Add the numerator
Step 3: Write result over original denominator
Example: Convert 3 2/5 to improper fraction
Step 1: 3 × 5 = 15
Step 2: 15 + 2 = 17
Step 3: 17/5
Answer: 3 2/5 = 17/5
Improper Fraction to Mixed Number
Step 1: Divide numerator by denominator
Step 2: Quotient = whole number
Step 3: Remainder = new numerator
Step 4: Denominator stays the same
Example: Convert 23/4 to mixed number
Step 1: 23 ÷ 4 = 5 remainder 3
Step 2: Whole number = 5
Step 3: Remainder = 3 (new numerator)
Step 4: Denominator = 4
Answer: 23/4 = 5 3/4
7. Rounding Mixed Numbers
Rounding Rule
Look at the FRACTION PART:
• If fraction ≥ 1/2 → ROUND UP
• If fraction < 1/2 → ROUND DOWN (stay same)
How to Check if Fraction ≥ 1/2
Compare: numerator ≥ (denominator ÷ 2)
If YES → Round up
If NO → Stay the same
Examples
Example 1: Round 7 3/4
Is 3/4 ≥ 1/2?
Half of 4 is 2
3 ≥ 2? Yes!
Round UP: 7 → 8
Answer: 8
Example 2: Round 12 1/3
Is 1/3 ≥ 1/2?
Half of 3 is 1.5
1 < 1.5
Round DOWN (stay same): 12
Answer: 12
Example 3: Round 9 5/8
Is 5/8 ≥ 1/2?
Half of 8 is 4
5 ≥ 4? Yes!
Round UP: 9 → 10
Answer: 10
Quick Reference: Fraction Formulas
Concept | Formula/Rule |
---|---|
Equivalent Fractions | a/b = (a×n)/(b×n) or (a÷n)/(b÷n) |
Simplify to Lowest Terms | Divide by GCF |
LCD | LCM of denominators |
Mixed to Improper | a b/c = (a×c+b)/c |
Improper to Mixed | Divide: quotient remainder/denominator |
Round Mixed Numbers | If fraction ≥ 1/2, round up |
💡 Important Tips to Remember
✓ Equivalent fractions: Multiply/divide numerator AND denominator by same number
✓ Lowest terms: Divide by GCF until no common factors remain
✓ LCD is needed for adding, subtracting, and comparing fractions
✓ Same denominator: Compare numerators (larger numerator = larger fraction)
✓ Same numerator: Compare denominators (smaller denominator = larger fraction)
✓ Different numerators and denominators: Convert to LCD first
✓ Mixed to improper: Multiply, add, keep denominator
✓ Improper to mixed: Divide, quotient is whole, remainder is numerator
✓ Rounding: Compare fraction to 1/2 (numerator vs half of denominator)
✓ Always simplify your final answer to lowest terms
🧠 Memory Tricks & Strategies
Equivalent Fractions:
"Whatever you do to the top, do to the bottom too!"
Simplifying:
"Find the GCF and divide it right - makes the fraction small and tight!"
Comparing Fractions:
"Same bottom? Compare the top! Same top? Smaller bottom is on top!"
Mixed to Improper:
"Multiply, add, and place - denominator stays in its space!"
Improper to Mixed:
"Divide to decide the whole, remainder's the goal!"
Rounding Mixed Numbers:
"Half or more? Raise the score! Less than half? Just laugh!"
Master Fractions! 🍕 ✨
Remember: Fractions are parts of a whole - practice makes perfect!