Fraction: A number representing part of a whole, written as numerator/denominator
Numerator: Top number showing parts taken
Denominator: Bottom number showing total equal parts
Proper Fraction: Value less than 1 (numerator < denominator)
Improper Fraction: Value greater than or equal to 1 (numerator ≥ denominator)
Mixed Number: Combination of whole number and proper fraction
Multiplication Rule: \(\frac{a}{b} \times \frac{c}{d} = \frac{a \times c}{b \times d}\)
Cross Simplification: Cancel common factors before multiplying
Identity Property: \(\frac{a}{b} \times 1 = \frac{a}{b}\)
Commutative Property: Order doesn't matter
Associative Property: Grouping doesn't matter
Zero Property: \(\frac{a}{b} \times 0 = 0\)
Basic Method: Multiply numerators, multiply denominators
Simplification: Reduce to lowest terms using GCD
Cross-Simplify: Cancel before multiplying
Conversion: Change mixed numbers to improper fractions
Verification: Check by reversing the operation
Estimation: Check if answer makes sense
Product Size: Usually smaller than original fractions
Common Factors: Always look for cross-simplification
Word Problems: "Of" means multiply
Real Applications: Recipes, measurements, sharing
Memorization: "Multiply across, simplify if possible"
Checking: Estimate to verify reasonableness
Answer Key
Step 1: Multiply numerators: \(1 \times 2 = 2\)
Step 2: Multiply denominators: \(4 \times 3 = 12\)
Step 3: Form result: \(\frac{2}{12}\)
Step 4: Simplify: \(\frac{2}{12} = \frac{1}{6}\)
Verification: Cross-check by decimal conversion: \(\frac{1}{4} = 0.25\), \(\frac{2}{3} = 0.667\), \(0.25 \times 0.667 = 0.167\), \(\frac{1}{6} = 0.167\) ✓
Answer: \(\frac{1}{6}\)
Always multiply numerators together and denominators together, then simplify if possible.
Step 1: Multiply numerators: \(3 \times 1 = 3\)
Step 2: Multiply denominators: \(5 \times 2 = 10\)
Step 3: Form result: \(\frac{3}{10}\)
Step 4: Check for simplification: GCD(3,10)=1, so already in lowest terms
Verification: \(\frac{3}{5} = 0.6\), \(\frac{1}{2} = 0.5\), \(0.6 \times 0.5 = 0.3\), \(\frac{3}{10} = 0.3\) ✓
Answer: \(\frac{3}{10}\)
If the GCD of numerator and denominator is 1, the fraction is already in its simplest form.
Step 1: Look for cross-simplification: \(\frac{2}{6} = \frac{1}{3}\)
Step 2: New multiplication: \(\frac{1}{3} \times \frac{3}{4}\)
Step 3: Cross-simplify again: \(\frac{1}{3} \times \frac{3}{4} = \frac{1}{1} \times \frac{1}{4}\)
Step 4: Final result: \(\frac{1}{4}\)
Verification: Direct multiplication: \(\frac{2 \times 3}{6 \times 4} = \frac{6}{24} = \frac{1}{4}\) ✓
Answer: \(\frac{1}{4}\)
Always cross-simplify before multiplying to make calculations easier and avoid large numbers.
Skill Progression
- Read carefully: Identify the fractions to be multiplied
- Look for simplification: Check if cross-simplification is possible
- Multiply: Multiply numerators and denominators
- Simplify: Reduce to lowest terms if necessary
- Check: Verify the answer makes sense
• Basic multiplication: \(\frac{a}{b} \times \frac{c}{d} = \frac{ac}{bd}\)
• With whole numbers: \(\frac{a}{b} \times n = \frac{an}{b}\)
• Mixed numbers: Convert to improper fractions first
• Cross-simplification: Cancel common factors before multiplying