How to Use the Proportion Solver
A proportion states that two ratios are equal: a:b = c:x. Using the cross-multiplication rule (a×x = b×c), you can solve for any unknown. Select which variable to find, enter the remaining three values, and the result appears instantly.
- Find x: x = (b × c) / a
- Find a: a = (b × c) / x
- Find b: b = (a × x) / c
- Find c: c = (a × x) / b
Example: If 2 inches on a map equals 50 miles, how far is 5 inches? → 2:50 = 5:x → x = 125 miles.
Frequently Asked Questions
Does this work with decimals?
Yes. Decimal and fractional inputs are fully supported for precise calculations.
Where is proportion used in real life?
Map scaling, recipe adjustments, currency conversion, similar triangle side lengths, and unit rate problems.
What if the divisor is zero?
Division by zero is undefined. The calculator will display an error and ask you to enter a nonzero value.