Last visit was: 19 Jul 2024, 21:56 It is currently 19 Jul 2024, 21:56

Close

GRE Prep 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 GRE 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.

Close

Request Expert Reply

Confirm Cancel
avatar
Intern
Intern
Joined: 17 Feb 2018
Posts: 2
Own Kudos [?]: 6 [3]
Given Kudos: 0
Send PM
Most Helpful Community Reply
avatar
Intern
Intern
Joined: 10 Sep 2018
Posts: 20
Own Kudos [?]: 62 [0]
Given Kudos: 0
Send PM
General Discussion
avatar
Intern
Intern
Joined: 27 Oct 2018
Posts: 49
Own Kudos [?]: 36 [0]
Given Kudos: 0
Send PM
avatar
Director
Director
Joined: 09 Nov 2018
Posts: 505
Own Kudos [?]: 131 [0]
Given Kudos: 0
Send PM
Re: Suppose n is a two-digit positive integer with units digit 5 [#permalink]
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.
avatar
Manager
Manager
Joined: 08 Dec 2018
Posts: 94
Own Kudos [?]: 69 [0]
Given Kudos: 0
Send PM
Re: Suppose n is a two-digit positive integer with units digit 5 [#permalink]
10U+5=n
So, E=[(10U+5)^2-25]/100
by calculation,E= U^2+U.
GRE Prep Club Tests Editor
Joined: 13 May 2019
Affiliations: Partner at MyGuru LLC.
Posts: 186
Own Kudos [?]: 325 [3]
Given Kudos: 5
Location: United States
GMAT 1: 770 Q51 V44
GRE 1: Q169 V168
WE:Education (Education)
Send PM
Re: Suppose n is a two-digit positive integer with units digit 5 [#permalink]
2
Expert Reply
1
Bookmarks
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.
avatar
Intern
Intern
Joined: 18 Sep 2023
Posts: 10
Own Kudos [?]: 12 [2]
Given Kudos: 3
Send PM
Re: Suppose n is a two-digit positive integer with units digit 5 [#permalink]
1
1
Bookmarks
n=10*u+5

(n^2-25)/100=[(n-5)*(n+5)]/100=(10*u+5-5)*(10*u+5+5)/100

=[10*u*(10*u+10)]/100

=10*u*10*(u+1)/100

=100*u*(u+1)/100

=u*(u+1)=u^2+u
Prep Club for GRE Bot
[#permalink]
Moderators:
GRE Instructor
49 posts
GRE Forum Moderator
26 posts
Moderator
1091 posts
GRE Instructor
218 posts

Powered by phpBB © phpBB Group | Emoji artwork provided by EmojiOne