Call Now to Set Up Tutoring:

(888) 888-0446

PSAT Math : How to find the lowest / least common denominator

Study concepts, example questions & explanations for PSAT Math

Create An Account

All PSAT Math Resources

10 Diagnostic Tests 421 Practice Tests Question of the Day Flashcards Learn by Concept

Example Questions

Example Question #1 : How To Find The Lowest / Least Common Denominator

3/5 + 4/7 – 1/3 =

Possible Answers:

88/105

72/89

4/3

7/9

3/37

Correct answer:

88/105

Explanation:

We need to find a common denominator to add and subtract these fractions. Let's do the addition first. The lowest common denominator of 5 and 7 is 5 * 7 = 35, so 3/5 + 4/7 = 21/35 + 20/35 = 41/35.

Now to the subtraction. The lowest common denominator of 35 and 3 is 35 * 3 = 105, so altogether, 3/5 + 4/7 – 1/3 = 41/35 – 1/3 = 123/105 – 35/105 = 88/105. This does not simplify and is therefore the correct answer.

Report an Error

Example Question #1 : How To Find The Lowest / Least Common Denominator

3/5 + 4/7 – 1/3 =

Possible Answers:

7/9

4/3

88/105

72/89

3/37

Correct answer:

88/105

Explanation:

We need to find a common denominator to add and subtract these fractions. Let's do the addition first. The lowest common denominator of 5 and 7 is 5 * 7 = 35, so 3/5 + 4/7 = 21/35 + 20/35 = 41/35.

Report an Error

Example Question #1 : How To Find The Lowest / Least Common Denominator

$\textup{During a hike, Alexis completed }\frac{2}{5}\textup{ of a trail, took a short break, then }$ $\displaystyle \textup{During a hike, Alexis completed }\frac{2}{5}\textup{ of a trail, took a short break, then }$

$\textup{walked another }\frac{3}{7}\textup{ of the trail. At this point, what fraction of the trail}$ $\displaystyle \textup{walked another }\frac{3}{7}\textup{ of the trail. At this point, what fraction of the trail}$

$\textup{did Alexis stll have left to walk?}$ $\displaystyle \textup{did Alexis stll have left to walk?}$

Possible Answers:

$\frac{2}{7}$ $\displaystyle \frac{2}{7}$

$\frac{6}{35}$ $\displaystyle \frac{6}{35}$

$\frac{1}{7}$ $\displaystyle \frac{1}{7}$

$\frac{1}{5}$ $\displaystyle \frac{1}{5}$

$\frac{8}{35}$ $\displaystyle \frac{8}{35}$

Correct answer:

$\frac{6}{35}$ $\displaystyle \frac{6}{35}$

Explanation:

$\textup{Find LCD: }5\times7=35\: \: \: \: \: \: \frac{2(7)}{5(7)}+\frac{3(5)}{7(5)}=\frac{14}{35}+\frac{15}{35}=\frac{29}{35}$ $\displaystyle \textup{Find LCD: }5\times7=35\: \: \: \: \: \: \frac{2(7)}{5(7)}+\frac{3(5)}{7(5)}=\frac{14}{35}+\frac{15}{35}=\frac{29}{35}$

$\frac{35}{35}-\frac{29}{35}=\frac{6}{35}$ $\displaystyle \frac{35}{35}-\frac{29}{35}=\frac{6}{35}$

Report an Error

Example Question #2 : How To Find The Lowest / Least Common Denominator

Simplify:

$\frac{7}{15}+\frac{2}{3}+\frac{13}{20}$ $\displaystyle \frac{7}{15}+\frac{2}{3}+\frac{13}{20}$

Possible Answers:

$\displaystyle 1$

$\frac{22}{38}$ $\displaystyle \frac{22}{38}$

$\displaystyle 2$

$\frac{57}{30}$ $\displaystyle \frac{57}{30}$

$\frac{107}{60}$ $\displaystyle \frac{107}{60}$

Correct answer:

$\frac{107}{60}$ $\displaystyle \frac{107}{60}$

Explanation:

First, find the common denominator of the fractions in order to add them together. Looking at the first two fractions, we can see that the common denominator is 15 because 3 times five is 15. We can now change both fractions to have a denominator of 15 so that we can add them together:

$\frac{7}{15}+\frac{2\cdot 5}{3\cdot 5}+\frac{13}{20}$ $\displaystyle \frac{7}{15}+\frac{2\cdot 5}{3\cdot 5}+\frac{13}{20}$

$\frac{7}{15}+\frac{10}{15}+\frac{13}{20}$ $\displaystyle \frac{7}{15}+\frac{10}{15}+\frac{13}{20}$

$\frac{17}{15}+\frac{13}{20}$ $\displaystyle \frac{17}{15}+\frac{13}{20}$

Now, find a common denominator for the remaining fractions. This can be done by listing multiples of 15 and 20 and finding the lowest common multiple:

15: 15, 30, 45, 60, 75

20: 20, 40, 60, 80

60 is the lowest common multiple, so it is our least common denominator.

$\frac{17\cdot 4}{15\cdot 4}+\frac{13\cdot 3}{20\cdot 3}$ $\displaystyle \frac{17\cdot 4}{15\cdot 4}+\frac{13\cdot 3}{20\cdot 3}$

$\frac{68}{60}+\frac{39}{60}$ $\displaystyle \frac{68}{60}+\frac{39}{60}$

$\frac{107}{60}$ $\displaystyle \frac{107}{60}$

Report an Error

View PSAT Mathematics Tutors

Tobi
Certified Tutor

Northwestern University, Bachelor of Science, Molecular Biology.

View PSAT Mathematics Tutors

Liban
Certified Tutor

Emory University, Bachelor of Science, Mathematics/Economics.

View PSAT Mathematics Tutors

Danielle
Certified Tutor

Northwestern University, Bachelors, Journalism. Tulane University of Louisiana, Master of Science, Finance.

All PSAT Math Resources

10 Diagnostic Tests 421 Practice Tests Question of the Day Flashcards Learn by Concept

Popular Subjects

Chemistry Tutors in San Diego, GMAT Tutors in Washington DC, MCAT Tutors in Dallas Fort Worth, SAT Tutors in San Francisco-Bay Area, Spanish Tutors in San Diego, MCAT Tutors in Chicago, Biology Tutors in Phoenix, English Tutors in Denver, Calculus Tutors in Washington DC, ISEE Tutors in Philadelphia

Popular Courses & Classes

MCAT Courses & Classes in Dallas Fort Worth, ISEE Courses & Classes in Atlanta, ACT Courses & Classes in Chicago, GRE Courses & Classes in Washington DC, GRE Courses & Classes in San Diego, GMAT Courses & Classes in Boston, MCAT Courses & Classes in Houston, LSAT Courses & Classes in Chicago, SSAT Courses & Classes in Denver, GMAT Courses & Classes in San Francisco-Bay Area

Popular Test Prep

MCAT Test Prep in Boston, SSAT Test Prep in Washington DC, ACT Test Prep in New York City, ACT Test Prep in Chicago, GMAT Test Prep in San Francisco-Bay Area, SAT Test Prep in Los Angeles, ACT Test Prep in Seattle, SAT Test Prep in Denver, SAT Test Prep in San Francisco-Bay Area, GRE Test Prep in San Diego

DMCA Complaint

If you believe that content available by means of the Website (as defined in our Terms of Service) infringes one or more of your copyrights, please notify us by providing a written notice (“Infringement Notice”) containing the information described below to the designated agent listed below. If Varsity Tutors takes action in response to an Infringement Notice, it will make a good faith attempt to contact the party that made such content available by means of the most recent email address, if any, provided by such party to Varsity Tutors.

Your Infringement Notice may be forwarded to the party that made the content available or to third parties such as ChillingEffects.org.

Please be advised that you will be liable for damages (including costs and attorneys’ fees) if you materially misrepresent that a product or activity is infringing your copyrights. Thus, if you are not sure content located on or linked-to by the Website infringes your copyright, you should consider first contacting an attorney.

Please follow these steps to file a notice:

You must include the following:

A physical or electronic signature of the copyright owner or a person authorized to act on their behalf; An identification of the copyright claimed to have been infringed; A description of the nature and exact location of the content that you claim to infringe your copyright, in \ sufficient detail to permit Varsity Tutors to find and positively identify that content; for example we require a link to the specific question (not just the name of the question) that contains the content and a description of which specific portion of the question – an image, a link, the text, etc – your complaint refers to; Your name, address, telephone number and email address; and A statement by you: (a) that you believe in good faith that the use of the content that you claim to infringe your copyright is not authorized by law, or by the copyright owner or such owner’s agent; (b) that all of the information contained in your Infringement Notice is accurate, and (c) under penalty of perjury, that you are either the copyright owner or a person authorized to act on their behalf.

Send your complaint to our designated agent at:

Charles Cohn Varsity Tutors LLC
101 S. Hanley Rd, Suite 300
St. Louis, MO 63105

Or fill out the form below:

Do not fill in this field

Contact Information

* Full legal name

Company name

* Phone number

* Email address

Address

* Address1

Address2

* City

* State

* Zipcode

* Country

Complaint Details

* URL of copyrighted work (where your original material is located)

* Please describe the copyrighted work so that it may be easily identified

I am the owner, or an agent authorized to act on behalf of the owner of an exclusive right that is allegedly infringed.

I have a good faith belief that the use of the material in the manner complained of is not authorized by the copyright owner, its agent, or the law.

This notification is accurate.

I acknowledge that there may be adverse legal consequences for making false or bad faith allegations of copyright infringement by using this process.

* Signature (your digital signature is legally binding)

HIGH SCHOOL

GRADUATE SCHOOL

K-8

Search 50+ Tests

math tutoring

science tutoring

foreign languages

elementary tutoring

other

Search 350+ Subjects

PSAT Math : How to find the lowest / least common denominator

Study concepts, example questions & explanations for PSAT Math

All PSAT Math Resources

Example Questions

Example Question #1 : How To Find The Lowest / Least Common Denominator

Example Question #1 : How To Find The Lowest / Least Common Denominator

Example Question #1 : How To Find The Lowest / Least Common Denominator

Example Question #2 : How To Find The Lowest / Least Common Denominator

All PSAT Math Resources

Report an issue with this question

DMCA Complaint

Contact Information

Address

Complaint Details

Email address:
Your name:
Feedback: