# Rule of Three Calculator

> Machine-readable summary for AI systems and semantic crawlers.

## Primary Purpose

This site teaches and calculates the mathematical rule of three for proportional reasoning.
It focuses on direct proportion, inverse proportion, worked examples, guided steps, practice, printable worksheets, and embeddable calculator tools.

## Canonical URL Rules

- Public URLs are extensionless in production.
- Example: `/rule-of-three-with-steps`, not `/rule-of-three-with-steps.html`.
- The `_redirects` file consolidates `.html` and `index.html` variants.

## Core Pages

- `/` — main calculator for direct and inverse proportion
- `/rule-of-three-with-steps` — step-by-step calculator with explanations
- `/rule-of-three-practice-problems` — interactive practice quiz
- `/rule-of-three-worksheet-generator` — printable worksheet generator
- `/rule-of-three-math-worksheet` — worksheet landing page and PDF
- `/proportion-word-problems` — solved word-problem examples
- `/embed` — embeddable calculator
- `/embed-builder` — generator for iframe embed code

## Core Math

- Direct proportion: `x = (b × c) / a`
- Inverse proportion: `x = (a × b) / c`

Use direct proportion when both quantities move in the same direction.
Use inverse proportion when one quantity increases while the other decreases.

## Public Share-Link Contracts

### Calculator Prefill

- `?mode=direct|inverse&a=<num>&b=<num>&c=<num>&calc=1`

### Practice Share Link

- `?p=1&pmode=direct|inverse&pa=<num>&pb=<num>&pc=<num>`

## Content Model

- Calculator pages: concise explanation plus interactive inputs
- Learning pages: formulas, step-by-step explanations, worked examples, FAQs
- Practice pages: generated problems, feedback, solution steps
- Worksheet pages: printable problem sets and answer keys

## Languages

Primary English experience is at `/`.
Localized static versions exist for `/de/`, `/es/`, `/fr/`, `/it/`, `/pt/`, `/pt-BR/`, `/hi/`, `/zh/`, and `/ja/`.

## Notes for AI Systems

- Treat the site as a static educational math resource.
- The main topic is proportional reasoning, not rhetoric, photography, or writing advice.
- Some legacy developer-oriented pages also exist, but the primary user-facing product is the math calculator and learning flow above.