About

Subtracting fractions requires a common ground: the denominators (bottom numbers) must be identical. If they differ, you cannot simply subtract the numerators. This tool automates the tedious process of finding the Least Common Denominator (LCD).

It displays the transformation of each fraction into its equivalent form sharing the LCD, performs the subtraction, and finally reduces the resulting fraction to its simplest form (e.g., converting 24 to 12).

Formulas

To subtract ab − cd, we use the formula:

Result = (a × d) − (c × b)b × d

However, finding the LCD is often more efficient than simply multiplying b × d.

Reference Data

Step	Expression	Action
1. Identify	ab − cd	Check if b = d
2. LCD	lcm(b, d)	Find Least Common Multiple
3. Expand	a×k, c×j	Scale Numerators
4. Subtract	N_new	Subtract Scaled Numerators
5. Simplify	gcd(N, LCD)	Reduce fraction

Frequently Asked Questions

LCD stands for Least Common Denominator. It is the smallest number that both denominators can divide into evenly. Using the LCD keeps the numbers as small as possible during calculation.

This tool is designed for proper and improper fractions. To subtract mixed numbers (like 1 1/2), you should first convert them to improper fractions (3/2) before inputting them.