What if a is 0 in the proportion solver?

Division by zero is undefined — the tool shows "Undefined (a = 0)" rather than a nonsensical number.

Math & Everyday

Ratio Calculator

Simplify a ratio to lowest terms, or solve a proportion.

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Simplifies a ratio to lowest terms, or solves a proportion for a missing term.

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How to use it

Choose "Simplify" to reduce a ratio to lowest terms, or "Solve a proportion" to find a missing term in a:b = c:x.
Enter the known values.
Read the result, with the working shown.

Formula

Simplify: divide both terms by gcd(a,b) · Solve: x = (b × c) ÷ a

Worked example

12:18 simplifies to 2:3. In the proportion 3:4 = 9:x, x = 12.

Interpreting your result

Simplification uses the same Euclidean-algorithm GCD as the GCF Calculator.

Frequently asked questions

Simplification uses the absolute value for the GCD step, so a negative ratio simplifies correctly, keeping the sign on the numerator.