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# Help with Proportions

A proportion occurs when two ratios are forced to be equal to each other. This selection will allow you to find a second ratio that is in the same proportion as the first.

Since a ratio is made up of two numbers, and a proportion compares 2 ratios, we ’ ll be dealing with 4 numbers here, 2 for each ratio.

• The first ratio will be between the two numbers represented by a and b. As a ratio, it will be a to b, or a:b. You can choose numbers for a and b below.

• The second ratio will be between the two numbers represented by c and d. As a ratio, it will be c to d, or c:d. You can choose numbers for c and d below.

The proportion below can be stated as: "a is to b as c is to d." This can also be written as a:b::c:d, or in frational form as a/b=c/d, which is how the fill in blanks appear below.

Here is the proportion:
 =

What can this form do?

• Type a number in all 4 boxes to see if you've formed a valid proportion.

• Type a number into 3 of the boxes, put a ? symbol into the 4th box, to see how to solve for the box containing the ? mark.

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