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Fractions & Mixed Numbers • Lesson 6 ⏱ 6 min read 📅 Updated Nov 2026

Least Common Denominator (LCD): How to Make Denominators the Same

Learn how to find the Least Common Denominator (LCD) using multiples and prime factorization so you can add and subtract fractions effortlessly.

Interactive Visual Math Explorer Explore Pizza & Fractions

Slice the pizza or slide the fraction bar to observe how fractions, decimals, and percentages relate in real time:

Interactive Visual Explorer

Denominator Alignment Visualizer

Try:
Core Rule

You cannot add apples and watermelons! Similarly, you cannot add 1/4 and 1/6 until you slice both pizzas into pieces of the exact same size. The LCD is simply the Least Common Multiple (LCM) of the denominators.

Multiples of 4: 4, 8, [12], 16, 20… Multiples of 6: 6, [12], 18, 24, 30… Least Common Multiple (LCD) = 12
Finding the LCD: The First Matching Number in Both Multiples Lists

Finding LCD: Step-by-Step for 1/4 and 1/6

  1. List multiples of each denominator:
    Multiples of 4: 4, 8, 12, 16, 20, 24…
    Multiples of 6: 6, 12, 18, 24, 30…
  2. Identify the smallest shared multiple: The LCD is 12.
  3. Convert both fractions to twelfths:
    1 × 34 × 3 = 312
    1 × 26 × 2 = 212
  4. Add with ease: 312 + 212 = 512.
Try It Yourself

Practice with Our Interactive GCF & LCM Calculator

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Solved Step-by-Step Examples:LCM of 6 and 81/4 + 1/6
Your Turn!

Check Your Understanding (3 Quick Questions)

Score: 0 / 3

Question 1: What is the LCD for 1/4 and 1/6?

Question 2: Why must denominators be equal before adding fractions?

Question 3: Convert 3/4 to twelfths: