This ratio calculator solves ratios or proportions in case a value is missing or even two values are missing or it can evaluate as true or false any ratio expression.

## How to use this ratio calculator?

- When you input two numbers (A and B) from the four of the ratio (decimals are allowed) you will get the complete and true ratio as the calculator will find the values for the rest of two numbers (C and D);

- When entering three numbers from the four available (A, B AND either C or D) you will discoverthe fourth one that was missing from the ratio;

- When you want to check whether the proportion is true or false you have to input all the components of the ratio (A, B, C, D) and you will get a message telling is TRUE or is FALSE.

The algorithm behind this ratio calculator is based on the following rules and formulas:

- IF only A and B are given then it multiplies A by 2 and B by 2 in order to calculate the C and D figure and have a true proportion;

- IF A, B and C are known to find D value it solves the expression in which D = C * (B / A). The same goes in case D is given and C is missing, case in which C = D * (A / B)

- IF all values are given (A, B, C, D) it will check if the expression is TRUE or FALSE through these steps: first it will calculate the value of the division of A by B (A/B) and the one of the division of C by D then it makes a comparison between the two. If they are equal then the ratio is TRUE, otherwise is FALSE.

## Example of calculations

1. A = 10, B = 6 and the results will consist of C=20 and D=12.

2. A = 7, B = 5 and C = 9 and the result will inform you that D=6.4285714285.

3. A = 13, B = 3 and D = 11 and you will discover that C=47.6666666666.

4. A = 34, B = 17, C = 3 and D = 23 is FALSE.

5. A = 20, B = 4, C = 15 and D = 3 is TRUE.