It is currently 25 Jun 2019, 12:11
My Tests

Close

GMAT Club Daily Prep

Thank you for using the timer - this advanced tool can estimate your performance and suggest more practice questions. We have subscribed you to Daily Prep Questions via email.

Customized
for You

we will pick new questions that match your level based on your Timer History

Track
Your Progress

every week, we’ll send you an estimated GMAT score based on your performance

Practice
Pays

we will pick new questions that match your level based on your Timer History

Not interested in getting valuable practice questions and articles delivered to your email? No problem, unsubscribe here.

Suppose n is a two-digit positive integer with units digit 5

  Question banks Downloads My Bookmarks Reviews Important topics  
Author Message
TAGS:
1 KUDOS received
Intern
Intern
Joined: 17 Feb 2018
Posts: 2
Followers: 0

Kudos [?]: 1 [1] , given: 0

Suppose n is a two-digit positive integer with units digit 5 [#permalink] New post 09 Sep 2018, 19:44
1
This post received
KUDOS
00:00

Question Stats:

69% (01:29) correct 30% (02:52) wrong based on 13 sessions
Suppose \(n\) is a two-digit positive integer with units digit 5, and tens digit u. Now, if \(E=\frac{(n^2-25)}{100}\), then express E in terms of u.

A. \(u+1\)

B. \(u^2+1\)

C. \(u^2-u\)

D. \(u^2+u\)

E. \(u^2+u+1\)

Here is how I did it:
E
=(n^2-25)/100
=[(n+5)(n-5)]/100
=[(u+1)*10*(u-1)*10]/100
=(u+1)(u-1)
=u^2-1, which is not an choice so I don't know where I did wrong.
5 KUDOS received
Intern
Intern
Joined: 10 Sep 2018
Posts: 20
Followers: 0

Kudos [?]: 16 [5] , given: 9

Re: Suppose n is a two-digit positive integer with units digit 5 [#permalink] New post 10 Sep 2018, 10:50
5
This post received
KUDOS
from the question, it can be said that n=10u+5.

now just plug it into the expression for E and then you'll get u^2+u after a little calculation.

answer D
Intern
Intern
Joined: 27 Oct 2018
Posts: 49
Followers: 0

Kudos [?]: 13 [0], given: 27

Re: Suppose n is a two-digit positive integer with units digit 5 [#permalink] New post 10 Nov 2018, 07:25
answer must be D only
n = 10u+5
Director
Director
Joined: 09 Nov 2018
Posts: 508
Followers: 0

Kudos [?]: 27 [0], given: 1

Re: Suppose n is a two-digit positive integer with units digit 5 [#permalink] New post 16 Nov 2018, 18:08
saifee wrote:
from the question, it can be said that n=10u+5.

now just plug it into the expression for E and then you'll get u^2+u after a little calculation.

answer D

Please provide clear explanation.
Manager
Manager
Joined: 08 Dec 2018
Posts: 76
Followers: 0

Kudos [?]: 25 [0], given: 24

CAT Tests
Re: Suppose n is a two-digit positive integer with units digit 5 [#permalink] New post 19 May 2019, 08:02
10U+5=n
So, E=[(10U+5)^2-25]/100
by calculation,E= U^2+U.
1 KUDOS received
MyGuru Representative
User avatar
Affiliations: Partner at MyGuru LLC.
Joined: 13 May 2019
Posts: 101
Location: United States
GMAT 1: 770 Q51 V44
GRE 1: Q169 V168
WE: Education (Education)
Followers: 1

Kudos [?]: 90 [1] , given: 2

CAT Tests
Re: Suppose n is a two-digit positive integer with units digit 5 [#permalink] New post 19 May 2019, 08:46
1
This post received
KUDOS
Expert's post
Quote:
Suppose \(n\) is a two-digit positive integer with units digit 5, and tens digit u. Now, if \(E=\frac{(n^2-25)}{100}\), then express E in terms of u.

A. \(u+1\)

B. \(u^2+1\)

C. \(u^2-u\)

D. \(u^2+u\)

E. \(u^2+u+1\)


Anytime you have a problem with variables in the choices and the problem, consider plugging in your own easy value(s) as an alternative to an often needlessly complex textbook algebraic approach. Easy values are going to be numbers that conform to the conditions of the problem, but are not themselves in the answer choices. In this case, I might consider plugging in n = 35, which in turn means that u = 3.

Subsequently, E = (35^2 - 25) / 100 = 12.

Now, plug u = 3 into each of the choices, testing all individually, seeking a match to the found value E = 12.

A. 3 + 1 ≠ 12 | Eliminate
B. 9 + 1 ≠ 12 | Eliminate
C. 9 - 3 ≠ 12 | Eliminate
D. 9 + 3 = 12 | Hold
E. 9 + 3 + 1 ≠ 12 | Eliminate

Select Choice D as the only match to the sought value of 12.
_________________

Stefan Maisnier


Director of Online Tutoring, MyGuru
www.myguruedge.com



Sign up today for a free 30-minute online GRE tutoring session!


Like us on Facebook
Watch us on YouTube
Follow us on Twitter
Follow us on Linkedin

Re: Suppose n is a two-digit positive integer with units digit 5   [#permalink] 19 May 2019, 08:46
Display posts from previous: Sort by

Suppose n is a two-digit positive integer with units digit 5

  Question banks Downloads My Bookmarks Reviews Important topics  


GRE Prep Club Forum Home| About| Terms and Conditions and Privacy Policy| GRE Prep Club Rules| Contact

Powered by phpBB © phpBB Group

Kindly note that the GRE® test is a registered trademark of the Educational Testing Service®, and this site has neither been reviewed nor endorsed by ETS®.