ISEE Middle Level Math : How to find a proportion

Study concepts, example questions & explanations for ISEE Middle Level Math

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Example Questions

Example Question #31 : Ratio And Proportion

If the ratio of boys to girls in a classroom is , and there are a total of of  students in the classroom, how many boys are in the classroom?

Possible Answers:

Correct answer:

Explanation:

If the ratio of boys to girls in a classroom is , that means that there are  boys for every  girls. Thus, when there are  students in a classroom, the breakdown will be  boys and  girls. If there are  students in a classroom, the breakdown will be  boys and  girls, which translates to a ratio of , or 

Thus, if there are  students,  will be boys. 

Example Question #32 : Ratio And Proportion

You survey  students about the plans for a new practice court for the basketball team and they must give a yes or no answer.  students are against the use of funds on this project.  What proportion of students said that they agreed with the plan?

Possible Answers:

Correct answer:

Explanation:

If  disagreed with the plan, that means the rest agreed.  

So to find that value, you must do the total minus the no's

.  

To find the proportion you must divide the part by the whole giving us an answer of  

.

Example Question #33 : Ratio And Proportion

If Mike gets two times the amount of work done than Joe, what is a ratio representing the work that each get done?

Possible Answers:

Correct answer:

Explanation:

Since Mike does twice the work that Joe does, his part of the ratio must be double the value of Joe's.  The only ratio given that has that is .

Example Question #34 : Numbers And Operations

Which statement does not follow from the statement  ?

Possible Answers:

Correct answer:

Explanation:

If , then:

The ratio of the numerators is equivalent to that of the denominators, in the same order. Hence,

 and  are true.

The reciprocals of the ratios are equivalent, so

However, it does not hold that 

.

This can be seen as follows:

.

 

Example Question #41 : Ratio And Proportion

Possible Answers:

Correct answer:

Explanation:

By a proportion property, if , it follows that .

Setting 

if , then .

Example Question #41 : Ratio And Proportion

Possible Answers:

Correct answer:

Explanation:

The cross-products (the product of a numerator and the other denominator) of a proportion are equal, so, if

, then

.

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