Math Problem Statement

How to find lowest common denominator

Solution

The lowest common denominator (LCD) is the smallest number that two or more denominators can all divide into without a remainder. It is essential when adding, subtracting, or comparing fractions. To find the LCD, follow these steps:

Step-by-Step Process:

  1. List the denominators: Write down the denominators of all fractions involved.

  2. Find the prime factors of each denominator: Break down each denominator into its prime factors. This helps in determining the least common multiple (LCM).

  3. Determine the LCM: Take the highest power of each prime factor that appears in any of the denominators.

  4. The LCM is the LCD: The least common multiple (LCM) of the denominators is the lowest common denominator.

Example:

Find the LCD of the fractions 26\frac{2}{6} and 38\frac{3}{8}.

  1. List the denominators: 6 and 8.

  2. Find the prime factors:

    • 6 = 2 × 3
    • 8 = 2 × 2 × 2
  3. Determine the LCM:

    • Take the highest power of each prime factor:
      • 232^3 (from 8) and 313^1 (from 6)
    • LCM = 23×31=8×3=242^3 \times 3^1 = 8 \times 3 = 24
  4. LCD: The lowest common denominator is 24.

So, 26\frac{2}{6} can be written as 824\frac{8}{24}, and 38\frac{3}{8} can be written as 924\frac{9}{24}.

Would you like to see more details or have any questions?


Related Questions:

  1. How can the lowest common denominator be used to simplify fractions?
  2. What are the differences between the LCM and the LCD?
  3. How do you find the LCD for more than two fractions?
  4. Why is it necessary to find the LCD when adding fractions?
  5. Can the LCD be a prime number?

Tip: Using prime factorization helps identify the LCD faster, especially for large numbers!

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Math Problem Analysis

Mathematical Concepts

Fractions
Prime Factorization
Least Common Multiple (LCM)

Formulas

LCM = Product of the highest powers of all prime factors

Theorems

Least Common Multiple Theorem

Suitable Grade Level

Grades 5-7