This proportion calculator can solve ratios in case a value is missing or even two values are missing from the given proportion or can evaluate as true or false any proportions.

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## How does this proportion calculator work?

This math tool allows you solve ratios in any of the following situations:

• By specifying two numbers (A and B in the first fraction area)  from the four numbers of the proportion (decimals are allowed) it will display the complete and true ratio by filling in the right values for the rest of two numbers (C and D);
• In case you input three numbers out of the four of the proportion (A, B AND either C or D) (decimals are allowed) it will display the ratio meaning that is returns the value for the number missing (C or D by case);
• Whenever you input all the components of the proportion it checks if the proportion is true or false.

The formulas used by this proportion calculator are:

• if you enter only A and B in order to determine the C and D figures, it multiplies both A and B by 2 in order to return true ratio values for C and D.
• if you complete the A, B and C to find the D value, it solves the expression in which D = C * (B / A). The same goes in case you input D and try to discover the C number.
• When all numbers are given (A, B, C, D) in order to assess whether the proportion is true or false it will calculate the value of the division of A by B (A/B), and the value of the division of C by D then compares it. If the two resulting values are equal then the ratio is TRUE, otherwise is FALSE.

## Few examples of calculations

1. A = 4, B = 9 then C = 8 and D = 18

2. A = 7, B = 13 and C = 6 then D = 11.1428571429

3. A = 28, B = 34 and D =15 then C= 12.3529411765

4. A = 13, B = 15, C = 2 and D = 33 then 13 : 15 = 2 : 33 is FALSE.

5. A = 11, B = 7, C = 29 and D = 18.4545454545 then 11 : 7 = 29 : 18.4545454545  is TRUE.

11 Apr, 2015