ISEE Lower Level Math : How to find a ratio

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

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Example Questions

Example Question #505 : Numbers And Operations

In a pet store, there are 12 cats and 9 dogs. Two-thirds of the cats are male, and one-third of the dogs are male. 

How many animals in the store are male?

Possible Answers:

Correct answer:

Explanation:

We can solve by multiplying the total number of animals by the fraction of males for each species.

Add these values together to find the total number of male animals.

Example Question #21 : Ratio And Proportion

Jenny has a collection of movies. She has 5 movies that are comedies and 10 movies that are dramas. What is the ratio of comedies to dramas that Jenny owns?

Possible Answers:

Correct answer:

Explanation:

A ratio is a relationship between two numbers such that there are as many items of the second number as there are of the first number. Given that for every 5 comedies that Jenny has, she has 10 dramas, the ratio between the two is . This reduces to , which is the correct answer. 

Example Question #21 : How To Find A Ratio

Gina owns 4 dogs and 2 cats. What is the ratio of dogs to cats?

Possible Answers:

Correct answer:

Explanation:

Given that there are 4 dogs and 2 cats, the ratio of dogs to cats is . However, this ratio can be be reduced to , which is therefore the correct answer. 

Example Question #22 : How To Find A Ratio

A coffee shop sells 2 types of pastries: cookies and muffins. There are 48 pastries for sale, and 16 of them are cookies. What is the ratio of cookies to muffins?

Possible Answers:

Correct answer:

Explanation:

If there are 48 pastries for sale, and 16 of them are cookies, that means that the remaining 32 pastries are muffins. 

Therefore, the ratio of cookies to muffins is , which is the same as . Therefore, 1:2 is the correct answer. 

Example Question #23 : How To Find A Ratio

If 30% of a class of 20 students are 5 years old, 20% are 7 years old, and the rest are 6 years old, what is the ratio 5 year-olds to 6 year-olds?

Possible Answers:

Correct answer:

Explanation:

If 30% of a class of 20 students are 5 years old, then that means there are six 5 year-olds. Given that 30% are 5 years old and 20% are 7 years old, the other 50% must be 6 years old. 

50% of 20 students is 10 students. 

Therefore, the ratio of 5 year-olds to 6 years-olds is . This can be reduced to .

Example Question #24 : How To Find A Ratio

In a class of 10 students, 60 percent are girls. What is the ratio of boys to girls?

Possible Answers:

Correct answer:

Explanation:

If 60 percent of the 10 students are girls, then 6 are girls and 4 are boys. Therefore, the ratio of boys to girls is . This reduces to , which is the correct answer. 

Example Question #511 : Numbers And Operations

Mark is trying to get the best deal on apples that he can. Which of the following is the best deal?

Possible Answers:

 apples for

 apples for

 apples for

 apples for

Correct answer:

 apples for

Explanation:

The best deal will be the one in which the ratio of apples to dollars is highest, as this means more apples can be purchased per a given dollar. 

The deal of  apples for  means that the ratio of apples to dollars is

This is the highest ratio compared to any of the other deals:

 apples for  has a ratio of apples to dollars of . The ratio of  is higher than the ratio of . ( and )

 apples for  has a ratio of apples to dollars of , but the ratio of  is higher than the ratio of  because the ratio of  can be rewritten as .

 apples for  has a ratio of apples to dollars of  or 

Therefore, the deal of  apples for  is the best one. 

Example Question #28 : How To Find A Ratio

Two girls and three boys get together for a picnic. Each girl brings three sandwiches to share, and each boy brings four mini desserts to share. What is the ratio of sandwiches to desserts at the picnic?

Possible Answers:

Correct answer:

Explanation:

If two girls and three boys get together for a picnic, and each girl brings three sandwiches to share, that means there will be six sandwiches at the picnic because .

If each boy brings four mini desserts to share, that means there will be twelve mini desserts at the picnic because

Therefore, the ratio of sandwiches to desserts at the picnic will be , which is equal to .

Example Question #22 : Ratio And Proportion

There are  girls and  boys in a class.  What is the ratio of boys to girls?

Possible Answers:

Correct answer:

Explanation:

A ratio is really nothing more than division. Many people will write it like this:

We can also write it like this:

Before being able to answer, you need to see if you can reduce this fraction—which you can! Go ahead and factor it into its primes:

You can cancel out a .  This leaves you with:

Therefore, the ratio is:

Example Question #511 : Numbers And Operations

There are 63 students at the assembly at ABC Elementary School. If there are only 21 boys at the assembly, what is the ratio (as a fraction) of the number of girls to the total amount of students at the assembly?

Possible Answers:

Correct answer:

Explanation:

The question is asking for the ratio of girls to the total amount of students at the assembly. If there are 21 boys, then there are 42 girls. The ratio is part to whole and would be represented as a fraction as:

This fraction can be reduced to simplest form by dividing the number and the denominator by the Greatest Common Factor or GCF, which is 21.  The correct answer is:

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