BREAKING: Target Test Prep releases Brand New 2026 On Demand GMAT prep course

Redeem
TTP OnDemand GMAT Video Course
Featured Course

Target Test Prep GMAT OnDemand

Scott Woodbury-Stewart’s private virtual classroom — 400 hours of master-class video lessons for the GMAT Focus Edition.

  • 715+ score guarantee — highest in the industry (99th percentile)
  • 52 chapters · 1,500+ lessons · 4,000+ practice questions
  • 400 hours of video · 1,500+ instructor-led HD smartboard lessons
  • 300,000+ students accepted to Harvard, Stanford, Wharton, Booth & Sloan & more
  • 24/7 live support + weekly Zoom office hours with GMAT instructors
  • TTP AI Assist — 24/7 AI-powered virtual tutor for instant help
  • 1,200+ flashcards + AI-powered study assistant & daily calendar
  • OnDemand, LiveTeach & GMAT Bootcamp formats available
  • Also: GRE, SAT Math & Executive Assessment courses
  • MBA Admissions Consulting now available
  • 🏆 2025 EdTech Breakthrough Award: Test Prep Solution Provider of the Year
  • 200,000+ students served
  • 5-day free trial — $0 to start, no auto-billing, cancel anytime
★★★★★ 5.0 (559 reviews)
130-pt guarantee
$0 to start then $127/mo
Start Free 5-Day Trial Read 559 Reviews →

What is the value of prime number z?

Expert replies
Post new topic Post Reply
Previous Topic Next Topic
Legendary Member
Posts: 1622
Joined: Thu Mar 01, 2018 7:22 amFollowed by: 2 members
by Gmat_mission » Mon Jun 25, 2018 12:12 am

Timer

00:00

Answers

A

B

C

D

E

Stats

Difficulty—

What is the value of prime number z?

(1) z^3 < 25
(2) z^2 > 1

[spoiler]OA=A[/spoiler].

Shouldn't be C the correct answer? I am confused. Please, someone help me.
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
Source: — Data Sufficiency |
Legendary Member
Posts: 2898
Joined: Thu Sep 07, 2017 2:49 pmFollowed by: 5 members
Thanked: 6 times

by Vincen » Mon Jun 25, 2018 12:40 am
Hello Gmat_mission.

First of all, we know that z is a prime number.

First Statement
(1) z^3 < 25
We have the following:

- If z=2 then z^3 = 8 < 25.
- If z=3, then z^3 = 27 > 25.

Therefore, the answer is z=2. So, this statement is sufficient.

Second Statement
(2) z^2 > 1
In this case, we have that any prime number z will satisfy that z^2 > 1. So, this statement is not sufficient.

Therefore, the correct answer is the option A.

I hope it helps you. <i class="em em-smiley"></i>
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
User avatar
GMAT Instructor
Posts: 15539
Joined: Tue May 25, 2010 12:04 pmFollowed by: 1906 members
Location: New York, NY
Thanked: 13060 times
GMAT Score:790

by GMATGuruNY » Mon Jun 25, 2018 2:33 am
Gmat_mission wrote:What is the value of prime number z?

(1) z^3 < 25
(2) z^2 > 1
Statement 1: z³ < 25
Only one value for z is possible:
z = 2, with the result that z³ = 2³ = 8.
If z is any other prime number, the value of z³ will exceed 25.
Thus, z=2.
SUFFICIENT.

Statement 2: z² > 1
Here, z can be ANY PRIME NUMBER, since the square of any prime number will be greater than 1.
Since the value of z cannot be determined, INSUFFICIENT.

The correct answer is A.
Private tutor exclusively for the GMAT and GRE, with over 20 years of experience.
Followed here and elsewhere by over 1900 test-takers.
I have worked with students based in the US, Australia, Taiwan, China, Tajikistan, Kuwait, Saudi Arabia -- a long list of countries.
My students have been admitted to HBS, CBS, Tuck, Yale, Stern, Fuqua -- a long list of top programs.

As a tutor, I don't simply teach you how I would approach problems.
I unlock the best way for YOU to solve problems.

For more information, please email me (Mitch Hunt) at [email protected].
Student Review #1
Student Review #2
Student Review #3
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
User avatar
GMAT Instructor
Posts: 1462
Joined: Thu Apr 09, 2015 9:34 amFollowed by: 22 members
Location: New York, NY
Thanked: 39 times

by Jeff@TargetTestPrep » Tue Jun 26, 2018 5:26 pm
Gmat_mission wrote:What is the value of prime number z?

(1) z^3 < 25
(2) z^2 > 1
Solution:

We are given that z is a prime number and we need to determine its value.

Statement One Alone:

z^3 < 25

Since the only prime whose cube is less than 25 is 2, then z must be 2 (notice that if z ≥ 3, then z^3 ≥ 27). Statement one alone is sufficient.

Statement Two Alone:

z^2 > 1

Since any prime number raised to the second power is greater than 1, z could be any prime number. Statement two alone is not sufficient.

Answer: A

Jeffrey Miller
Head of GMAT Instruction
[email protected]

Image

See why Target Test Prep is rated 5 out of 5 stars on BEAT the GMAT. Read our reviews
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
Post new topic Post Reply
• Page 1 of 1