Proportion


 
 
Concept Explanation
 

Proportion

Proportion:

A proportion is really two ratios that are equivalent to each other. Here is an example: There are several ways to tell if two ratios form a proportion.

1st method: Check to see if the same scale factor was used on top and bottom.  

2nd method: Try and simplify one or both of the ratios. In this example, we could reduce the second ratio. Check it out: Once again, we can see that the two ratios are equivalent. Therefore, they must form a proportion.  

3rd method: Cross products: Multiply the numbers that are diagonal to each other. If the products are equal, the two ratios form a proportion. 5 x 28 = 140 7 x 20 = 140 Check out what happens when you do not have a proportion: 2 x 45 = 90 3 x 28 = 84 Here, the cross products are not the same. This shows that the two ratios are not a proportion. These steps are also useful in finding the missing number in a proportion.  

Illustration: Here are some examples of finding the missing number in a proportion using all three methods.

1.)  

Sample Questions
(More Questions for each concept available in Login)
Question : 1

Determine if the following are in proportion : 4, 6, 8, 12

Right Option : B
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Explanation
Question : 2

Which of the following are in proportion?

Right Option : B
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Explanation
Question : 3

Determine if the following are in proportion : 11, 121, 9, 99

Right Option : A
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Explanation
 
 
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