A proportion calculator is a tool that helps you solve proportion problems. A proportion is a statement that two ratios are equal.

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The formula for proportion is:

a:b = c:d

where "a" and "b" are the first ratio, and "c" and "d" are the second ratio. In a proportion, the ratio of the first term to the second term is equal to the ratio of the third term to the fourth term.

## What is Proportion?

In mathematics, proportion refers to the relationship between two ratios that are equal to each other. A proportion is a statement of equality between two ratios, which are usually written as fractions. It expresses the relationship between the part and the whole or between two parts. The general form of a proportion is:

a/b = c/d

Where a and b are the first ratio, and c and d are the second ratio. The proportion states that the first ratio is equal to the second ratio. Proportions can be used to solve various problems related to ratios and proportions in different fields such as mathematics, science, and finance.

## Proportion Formula

The proportion formula is:

a/b = c/d

Where:

- a and b are the first pair of proportional values
- c and d are the second pair of proportional values

This can also be written as:

a : b = c : d

or

a/b = d/c

The cross-multiplication property can also be used to find the missing value in a proportion. For example, if we know a, b, and c, we can find d using the formula:

d = (b * c) / a

## Cross Multiplication for Solving Proportions

Cross multiplication is a method used to solve proportions, particularly those involving two ratios that are equal to each other. The steps for using cross multiplication to solve a proportion are as follows:

- Write the proportion as two equal fractions, with one fraction on each side of the equal sign.
- Cross-multiply by multiplying the numerator of one fraction by the denominator of the other fraction.
- Simplify the resulting equation by multiplying or dividing both sides by the same factor, if necessary.
- Solve for the variable by isolating it on one side of the equation.

Here’s an example:

Solve for x: 3/5 = 9/x

- Write the proportion: 3/5 = 9/x
- Cross-multiply: 3x = 45
- Simplify: divide both sides by 3, x = 15
- Check: substitute x = 15 back into the original equation to make sure both sides are equal: 3/5 = 9/15 = 3/5