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Mastering Fraction Multiplication and Division

Aug 14, 2024

Multiplying and Dividing Fractions Lecture Notes

Multiplying Fractions

  • Basic Process:

    • Multiply the numerators together.
    • Multiply the denominators together.
  • Example 1: 7/15 x 3/4

    • Multiply numerators: 7 x 3 = 21
    • Multiply denominators: 15 x 4 = 60
    • Result: 21/60
    • Simplify: Divide by common factor of 3 to get 7/20
  • Example 2: 4/7 x 9/5

    • Multiply numerators: 4 x 9 = 36
    • Multiply denominators: 7 x 5 = 35
    • Result: 36/35 (No simplification needed)
  • Multiplying by Mixed Numbers:

    • Convert mixed numbers to improper fractions.
    • Example: Multiply 4/5 by 2 3/4
      • Convert 2 3/4 to improper fraction: (2 x 4) + 3 = 11/4
      • Multiply: 4/5 x 11/4
      • Result: 44/20
      • Simplify: Divide by common factor of 4 to get 11/5
  • Fractions Less Than One:

    • Multiplying fractions less than one results in a smaller number.
    • Example: 1/2 x 1/3 = 1/6

Dividing Fractions

  • Basic Process:

    • Write the division problem as a multiplication problem by flipping the second fraction (take the reciprocal).
    • Change the division sign to multiplication.
  • Example 1: 3/4 ÷ 5/9

    • Flip the second fraction: 9/5
    • Change to multiplication: 3/4 x 9/5
    • Multiply: 3 x 9 = 27, 4 x 5 = 20
    • Result: 27/20 (No simplification needed)
  • Example 2: 2/3 ÷ 4/5

    • Flip the second fraction: 5/4
    • Change to multiplication: 2/3 x 5/4
    • Multiply: 2 x 5 = 10, 3 x 4 = 12
    • Result: 10/12
    • Simplify: Divide by common factor of 2 to get 5/6
  • Dividing Mixed Numbers:

    • Convert mixed numbers to improper fractions first.
    • Example: 3 1/2 ÷ 2/5
      • Convert 3 1/2 to improper: (3 x 2) + 1 = 7/2
      • Flip second fraction: 5/2
      • Change to multiplication: 7/2 x 5/2
      • Multiply: 7 x 5 = 35, 2 x 2 = 4
      • Result: 35/4
      • Convert to mixed number: 8 3/4

Conclusion

  • Understanding how to multiply and divide fractions involves straightforward steps of basic arithmetic and conversion between mixed and improper fractions.
  • Simplification is often necessary to obtain the final answer in simplest form.
  • Practice these steps to master fraction operations.