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Find a missing value in an equivalent ratio

An equivalent ratio represents the same multiplicative relationship between two positive quantities: both terms are multiplied or divided by the same nonzero scale factor. Finding a missing term involves identifying that factor through a ratio table, double number line, or equation such as a:b=c:xa:b=c:x, and recognizing that adding the same amount to both terms does not preserve equivalence; the focus is numerical proportional reasoning with accessible whole-number, decimal, and fraction values, not generalized algebraic cases.

Detailed Explanation: Find a missing value in an equivalent ratio

An equivalent ratio keeps the same multiplicative relationship between the two quantities. To find a missing value, find the factor that changes one known term into its matching term, then use that same factor on the other term.

Example: Find xx.

3:5=12:x3:5 = 12:x
  1. Compare the first terms: 33 becomes 1212.

3×4=123 \times 4 = 12

So, the scale factor is 44.

  1. Multiply the other term by the same factor:

5×4=205 \times 4 = 20
  1. Therefore,

x=20x=20

So the equivalent ratios are

3:5=12:203:5 = 12:20

Check: Both terms in 3:53:5 were multiplied by 44. Adding the same number would not work because equivalent ratios are made by multiplying or dividing both terms by the same factor.

Learn by doing: Find a missing value in an equivalent ratio

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Ratios - Equivalent, Expanding Recipes with Non-Integer Multiples - Whole Numbers


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