Intermediate Test Prep (Grade 6) Verify the proportionality using the product of the means equals the product of the extremes

Proportionality
Lesson
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A proportion is an equation which states that two ratios are equivalent.

In the proportion r/s = x/y the values of the s and x are know as the means. The values of the r and y are known as the extremes.
If the product of the means is equivalent to the product of the extremes then the ratios are a proportion.

Find the cross product
	Compare the products
		If they are equal
			They are proportions!

Example
1/2 = 5/10
To determine whether or not each pair of ratios is a proportion use the product of the means equal to the product of the extremes.
2 x 5 = 10 1 x 10 = 10 The cross products are equivalent, therefore this is a proportion.

It is important to remember that a proportion states that two ratios are equal. Therefore, the units need to be the same and the cross products have to be equal for the ratios to form a proportion.

Sample Problems

2/3 = 1/5
Use cross products		2 x 5 = 10 and 3 x 1 = 3
Compare		2/3 and 1/5 are not equal
*Answer:*		not proportional

3/4 = 9/12
Use cross products		3 x 12 = 36 and 4 x 9 = 36
Compare		3/4 and 9/12 are equal
Answer:		proportional

Let's Practice!

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