Proportion Calculator
A proportion says two ratios are equal: a/b = c/d. Enter the three values you know, pick which term is missing, and the calculator solves it by cross multiplication.
Your numbers
Result
- Completed proportion
- 2 / 3 = 8 / 12
| Step | Detail |
|---|---|
| Proportion | a / b = c / d, solving for d |
| Cross multiply | a x d = b x c |
| Result | d = 12 |
How to solve a proportion
In a/b = c/d, the cross products are equal: a x d = b x c. To find a missing term, rearrange. For 2/3 = 8/d, cross multiply to 2d = 24, so d = 12. Whichever term you leave out, the calculator solves it the same way.
Why proportions are everywhere
Proportions scale recipes, maps, models and mixtures, and convert between units. They are the idea behind the rule of three and behind reading a scale like "1 inch = 50 miles". If two quantities keep the same ratio, a proportion finds any missing value.
Frequently asked questions
Sources
- Ratios and proportions (cross multiplication)
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