How to Determine if a Proportional Relationship Exists Between Two Quantities

Determining a proportional relationship requires you to complete a few key steps. Determine if a proportional relationship exists between two quantities with help from a mathematician and educator in this free video clip.

Part of the Video Series: Algebra Help

Video Transcript

Hi, my name is Marija and I'm a mathematician and today I'm going to tell you how to determine whether or not a proportional relationship exists between two quantities. So, if the two quantities you are given are five over seven and two over three, and you want to know whether or not there's a proportional relationship. Well, the easiest way to find out is to simply cross-multiply and then compare products. So, I'm going to cross-multiply this denominator times this numerator and when I do that three times five is fifteen. And then I'm going to cross-multiply this denominator times this numerator and when I do that, seven times two is fourteen and now all I have to do is look at the products. Over here I have fifteen. Over here I got fourteen. Are they equal? No. Therefore these are not equal. So, while they're very close in, in quantity they're not the same, therefore these two ratios do not have a proportional relationship. So, easiest way to tell if two quantities have a proportional relationship is to cross-multiply and then compare their products and that's it.

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