ACT Math : Proportion / Ratio / Rate

Study concepts, example questions & explanations for ACT Math

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Example Questions

Example Question #54 : Proportion / Ratio / Rate

When television remotes are shipped from a certain factory, 1 out of every 200 is defective. What is the ratio of defective to nondefective remotes?

Possible Answers:

1:199

199:1

200:1

1:200

Correct answer:

1:199

Explanation:

One remote is defective for every 199 non-defective remotes.

Example Question #55 : Proportion / Ratio / Rate

On a desk, there are  papers for every  paper clips and  papers for every  greeting card. What is the ratio of paper clips to total items on the desk?

Possible Answers:

Correct answer:

Explanation:

Begin by making your life easier: presume that there are  papers on the desk. Immediately, we know that there are  paper clips. Now, if there are  papers, you know that there also must be  greeting cards. Technically you figure this out by using the ratio:

By cross-multiplying you get:

Solving for , you clearly get .

(Many students will likely see this fact without doing the algebra, however. The numbers are rather simple.)

Now, this means that our desk has on it:

 papers

 paper clips

 greeting cards

Therefore, you have  total items.  Based on this, your ratio of paper clips to total items is:

, which is the same as .

Example Question #1 : How To Express A Fraction As A Ratio

In a classroom of  students, each student takes a language class (and only one—nobody studies two languages).  take Latin,  take Greek,  take Anglo-Saxon, and the rest take Old Norse. What is the ratio of students taking Old Norse to students taking Greek?

Possible Answers:

Correct answer:

Explanation:

To begin, you need to calculate how many students are taking Old Norse. This is:

Now, the ratio of students taking Old Norse to students taking Greek is the same thing as the fraction of students taking Old Norse to students taking Greek, or:

Next, just reduce this fraction to its lowest terms by dividing the numerator and denominator by their common factor of :

This is the same as .

Example Question #2 : How To Express A Fraction As A Ratio

In a garden, there are  pansies,  lilies,  roses, and  petunias. What is the ratio of petunias to the total number of flowers in the garden?

Possible Answers:

Correct answer:

Explanation:

To begin, you need to do a simple addition to find the total number of flowers in the garden:

Now, the ratio of petunias to the total number of flowers in the garden can be represented by a simple division of the number of petunias by . This is:

Next, reduce the fraction by dividing out the common  from the numerator and the denominator:

This is the same as .

Example Question #1 : How To Find Proportion

Max will be age X in 5 years. How old was he 4 years ago?

 

Possible Answers:

X – 5

X +5

X – 9

X – 4

Correct answer:

X – 9

Explanation:

Max will be X in 5 years. So today he is X -5 and 4 years ago he was (X-5)  - 4, that is X – 9.  It always helps to put numbers into the equations. Example: Max will be 12 in 5 years. How old was he 4 years ago? So today Max is 12 – 5 = 7.  Therefore, four years ago he was 7 -4 =3. Which is 12-5-4 =12-9 = 3

 

Example Question #2 : How To Find Proportion

If a pizza pie that has 16 slices and costs $12.00 is to be shared among 8 friends, how much should each person contribute?

 

Possible Answers:

$1.75

$1.50

$2

$0.75

Correct answer:

$1.50

Explanation:

It is $12 divided by 8 which is $1.50. The number of slices in the pizza pie is not relevant in this question.

 

Example Question #41 : Proportion / Ratio / Rate

In a school relay race, every 5-man team must sprint 110 yards total.  However, Jim’s team is short a person.  Thus, Jim must run two sections for his team.  How far does Jim have to run?

 

Possible Answers:

27.5 yards

22 yards

45.4 yards

44 yards

110 yards

Correct answer:

44 yards

Explanation:

 We first find out how much each person must run.  Thus we take 110/5 to get 22 yards.  However, Jim must run twice the amount of a normal competitor, so we multiply by 2 to get 44 yards.

 

 

 

Example Question #4 : How To Find Proportion

A building that is 30 feet tall casts a shadow that is 50 feet long. If another building casts a shadow that is 100 feet long, how tall is the building?

Possible Answers:

1670 feet

167 feet

6 feet

600 feet

60 feet

Correct answer:

60 feet

Explanation:

This problem can be set up as a proportion: 30 feet/x feet = 50 feet/100 feet. To solve, we simply cross multiply: (30 feet * 100 feet) = (50 feet * x feet). Thus, 3000 feet = 50x feet. To solve for x, divide each side by 50. Therefore, = 60 feet.  If you got 167 feet, you may have set up the proportion incorrectly by mixing up the height of the building with the length of the shadow. If you got 6 feet or 600 feet, you may have made a computational error. If you got 1670 feet, you may have set the proportion up incorrectly and made a computational error.

 

Example Question #1 : How To Find Proportion

If a bicyclist can bike 24 miles per hour, how far (in miles) can he travel in 2 minutes, assuming he bikes at a constant speed (answer rounded to the nearest tenth)?

Possible Answers:

0.8

0.75

1.0

2.0

0.5

Correct answer:

0.8

Explanation:

0.8 mile.  Using some conversions:  ( (24mi/1hr)*(1hr/60min)*2min = 0.8 mile

Example Question #42 : Proportion / Ratio / Rate

If 10,000 lbs of cement makes 85,000 lbs of concrete, how many pounds of concrete can be made with 3,000 pounds of cement?

Possible Answers:

25,500

30,000

363

10,000

12,230

Correct answer:

25,500

Explanation:

25,500 lbs of concrete. Setting up a ratio with x representing the number of pounds concrete the 3,000 of cement produces, we obtain the relation: (10,000/85,000) = (3,000/x), x = 25,500 pounds of concrete.

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