Cross Multiplication
Cross Multiplication — solve proportions of the form a/b = c/d. Given any three values, find the fourth.
Formula
a/b = c/d → d = (b × c) / a
- Cross multiplication solves proportions: a/b = c/d
- If d = 0 (input), the calculator solves for d
- Otherwise, it verifies the proportion and shows both ratios
Cross Multiplication Example
Inputs
- a (numerator 1): 2
- b (denominator 1): 3
- c (numerator 2): 4
- d (denominator 2, or 0 to solve): 0
Given 2/3 = 4/d, find d. Using cross multiplication: d = (3 × 4) / 2 = 6. So 2/3 = 4/6.
Frequently asked questions
What is cross multiplication?
Cross multiplication is a method to solve proportions (a/b = c/d) by multiplying diagonals: a × d = b × c.
When should I use this calculator?
Use it when you need to solve proportions, find missing values in ratios, or verify if two ratios are equivalent.
How do I solve for d?
Enter values for a, b, c and set d = 0. The calculator will compute d = (b × c) / a.
What if I want to verify a proportion?
Enter all four values a, b, c, d. The calculator will show both ratios and whether they're equal.