Proportion Calculator FAQ
What does this proportion calculator do?
It solves both direct proportion and inverse proportion problems. When you enter any three known values, the calculator finds the missing fourth value.
What is the rule of three?
The rule of three is a basic method for solving proportional relationships. In direct proportion, the ratios stay equal. In inverse proportion, the product of the paired values stays constant.
How do you solve a direct proportion by cross multiplication?
Start from a / b = c / d. Cross multiplication gives a × d = b × c. From there, solve for the unknown variable, for example d = (b × c) / a.
How does inverse proportion work?
Inverse proportion uses a × b = c × d. This is useful when one value increases while the other decreases, such as workers and time, speed and travel time, or price per unit and quantity at a fixed total.
What kinds of problems can I solve with this calculator?
You can use it for scaling recipes, price-per-unit comparisons, map scale problems, quantity planning, work-time problems, speed-time tradeoffs, and other direct or inverse ratio problems.
