Your All-in-One Proportion Tool: You Rule The 3!
If 2 apples cost $6, how much do 5 apples cost?
Use the calculator below to solve any similar problem
A Rule of Three calculator helps you solve proportional problems using three known values to find an unknown fourth value. You'll use the formula a/b = c/x, where x represents your unknown quantity. This mathematical tool works for both direct proportions (quantities increasing together) and inverse proportions (quantities moving oppositely). Once you understand the basic formula, you'll discover how this simple calculation method transforms complex real-world problems into manageable solutions.
Use this when quantities increase or decrease in the same proportion.
Formula: x = (b × c) ÷ a
Use this when quantities change in opposite directions.
Formula: x = (a × b) ÷ c
Mastering the Rule of Three calculator begins with a simple four-step sequence that'll help you solve proportion problems efficiently.
You'll locate your unknown value by following these essential steps:
Getting accurate results with the Rule of Three calculator depends on three critical practices you'll want to follow.
First, verify your input values carefully before attempting to find a fourth number.
Second, understand whether your problem requires direct or inverse proportion.
Third, select the appropriate decimal precision that matches your calculation needs.
When tackling complex calculations, you'll discover that advanced Rule of Three techniques reveal powerful solutions for multi-variable problems.
To find any unknown value, you'll need to master both direct and inverse proportions, especially when dealing with compound relationships.
Three practical scenarios demonstrate how the Rule of Three calculator streamlines everyday calculations.
When you're shopping, it helps find the unknown value of 8 apples if 5 apples cost 10 euros.
In project management, it can determine how quickly 8 workers complete a task compared to 5 workers.
The Rule of Three simplifies these real-world proportions to accelerate decision-making.
Download our comprehensive worksheet designed to help teach the Rule of Three concept. This educational resource includes:
Perfect for classroom exercises, homework assignments, or home learning.
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Picture solving a puzzle: you'll use three known values to find a missing fourth. The rule of three helps you solve proportional relationships by setting up an equation where you multiply and divide your values.
You'll use rule of three computation to find an unknown value when you have three known values. It's based on proportions where you can solve direct or inverse relationships between quantities.
Quick as lightning, you'll solve proportions using three known values to find an unknown fourth. You're simply setting up equal ratios, where a/b = c/x, to calculate your missing number.
To find 3's power on your calculator, press "3," then hit the exponent button (usually "^" or "x^y"), enter your desired power number, and press equals to get your result.