Proportion Solver with Cross Multiplication Steps
Solve proportions and missing values using step-by-step cross multiplication.
Cross multiply: multiply the outer and inner terms
Enter three known values in a proportion a:b = c:d. Select which value is unknown.
How to use this calculator
Enter the proportion as a:b = c:d with one value unknown. Use x for the unknown. The calculator solves using cross multiplication.
What this means in math class
Cross multiplication is the standard method for solving proportions. Every 7th-grade student learns this for finding missing values.
Worked examples
Example 1: Solve for x
3:4 = 6:x
- Step 1:Cross multiply: 3 × x = 4 × 6
- Step 2:3x = 24
- Step 3:Divide both sides by 3: x = 8
Example 2: Real-world proportion
2 cups flour makes 24 cookies. How many cups for 60 cookies? 2:24 = x:60
- Step 1:Cross multiply: 2 × 60 = 24 × x
- Step 2:120 = 24x
- Step 3:Divide by 24: x = 5
Frequently asked questions
What is cross multiplication?
Multiplying across the equals sign in a proportion: a:b = c:d gives a×d = b×c.
Can I solve proportions with fractions?
Yes. Treat fractions as ratios. Cross multiplication works the same way.
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