Why is it when you have two equivalent fractions, their cross products are equal? Is there a good illustration/explanation of this that I could explain to a seventh grader?

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- Jun 26th 2012, 10:21 AMJman115Proportionality
Why is it when you have two equivalent fractions, their cross products are equal? Is there a good illustration/explanation of this that I could explain to a seventh grader?

- Jun 26th 2012, 12:33 PMemakarovRe: Proportionality
This follows from the fact that for all rational numbers x, y and z, if x = y, then xz = yz. So, we start with and and multiply both sides of by . It follows that . Since and , we get .