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Calculators » Math » Proportion - Missing Number

Our online tools will provide quick answers to your calculation and conversion needs. On this page, you can calculate missing number in a proportion. We have made it easy for you to enter numbers that are either directly proportional or inversely proportional to one another.

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Directly proportional numbers increase or decrease in equal proportions. if a ∝ b, then a = kb, or, a/b = k where k is constant. Therefore, a_{1} / b_{1} = a_{2} / b_{2}.

In inverse proportion, if one number increases, the other decreases and vice versa so that the product of the two numbers remains constant. if a ∝ 1/b, then a×b = k and therefore, a_{1} × b_{1} = a_{2} × b_{2}. To express in ratios, the variables can be re-arranged as to give a_{1} / a_{2} = b_{2} / b_{1} or a_{1} / b_{2} = a_{2} / b_{1
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