GMAT Question of the Day - Daily to your Mailbox; hard ones only

 It is currently 23 Oct 2018, 15:43

### 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

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

# GMAT.QR.0300 Book Question: 300

 new topic post reply Question banks Downloads My Bookmarks Reviews Important topics
Author Message
Intern
Joined: 16 May 2017
Posts: 34
Location: India
GMAT.QR.0300 Book Question: 300  [#permalink]

### Show Tags

19 Nov 2017, 06:54
GMAT.QR.0300
Book Question: 300

If a and b are positive integers, is a b 3 an integer?

a is an integer.
b = a
A. Statement (1) ALONE is sufficient, but statement (2) alone is not sufficient.
B. Statement (2) ALONE is sufficient, but statement (1) alone is not sufficient.
C. BOTH statements (1) and (2) TOGETHER are sufficient, but NEITHER statement ALONE is sufficient.
D. EACH statement ALONE is sufficient.
E. Statements (1) and (2) TOGETHER are not sufficient.

Explanation in Wiley's website :

C -You Answered Incorrectly.
Arithmetic Properties of numbers

Given that a is an integer, then a = 4 is possible. If, in addition b = 1, then a b 3 = 4 3 is not an integer. However, if, in addition b = 2, then a b 3 = 8 3 = 2 is an integer; NOT sufficient.
Given that b = a , then a b 3 = a a 3 = a 3 3 = a 3 3 = a = b is an integer; SUFFICIENT.
Statement 2 alone is sufficient.

Hi can someone explain to me, what is the logic? I did not get this one!

thanks
Math Revolution GMAT Instructor
Joined: 16 Aug 2015
Posts: 6406
GMAT 1: 760 Q51 V42
GPA: 3.82
Re: GMAT.QR.0300 Book Question: 300  [#permalink]

### Show Tags

20 Nov 2017, 23:06
bapism07 wrote:
GMAT.QR.0300
Book Question: 300

If a and b are positive integers, is a b 3 an integer?

a is an integer.
b = a
A. Statement (1) ALONE is sufficient, but statement (2) alone is not sufficient.
B. Statement (2) ALONE is sufficient, but statement (1) alone is not sufficient.
C. BOTH statements (1) and (2) TOGETHER are sufficient, but NEITHER statement ALONE is sufficient.
D. EACH statement ALONE is sufficient.
E. Statements (1) and (2) TOGETHER are not sufficient.

Explanation in Wiley's website :

C -You Answered Incorrectly.
Arithmetic Properties of numbers

Given that a is an integer, then a = 4 is possible. If, in addition b = 1, then a b 3 = 4 3 is not an integer. However, if, in addition b = 2, then a b 3 = 8 3 = 2 is an integer; NOT sufficient.
Given that b = a , then a b 3 = a a 3 = a 3 3 = a 3 3 = a = b is an integer; SUFFICIENT.
Statement 2 alone is sufficient.

Hi can someone explain to me, what is the logic? I did not get this one!

thanks

The original question is found as follows.

If a and b are positive integers, is $$\sqrt[3]{ab}$$ an an integer?

(1) $$\sqrt{a}$$ is an integer
(2) $$b=\sqrt{a}$$

Your solution for the condition 1) is correct.
Solution for the condition 2) is as follows.

Since $$b=\sqrt{a}$$, we have $$a = b^2$$.
$$\sqrt[3]{ab} = \sqrt[3]{b^2 \cdot b} = \sqrt[3]{b^3} = b$$
Thus this is sufficient.
_________________

MathRevolution: Finish GMAT Quant Section with 10 minutes to spare
The one-and-only World’s First Variable Approach for DS and IVY Approach for PS with ease, speed and accuracy.
"Only \$99 for 3 month Online Course"
"Free Resources-30 day online access & Diagnostic Test"
"Unlimited Access to over 120 free video lessons - try it yourself"

Intern
Joined: 16 May 2017
Posts: 34
Location: India
Re: GMAT.QR.0300 Book Question: 300  [#permalink]

### Show Tags

03 Dec 2017, 02:45
Hey math revolution

Actually, i was practicing the OG questions through the website gmat.wiley.com. There few of the special characters (like boldface characters for RC & CR questions, square root, fractions and few decimals were not viewed or viewed in a collapsed manner for DS and PS questions. I had informed them through message and they replied that they are working on it.
Re: GMAT.QR.0300 Book Question: 300 &nbs [#permalink] 03 Dec 2017, 02:45
Display posts from previous: Sort by

# GMAT.QR.0300 Book Question: 300

 new topic post reply Question banks Downloads My Bookmarks Reviews Important topics

Moderator: souvonik2k

 Powered by phpBB © phpBB Group | Emoji artwork provided by EmojiOne Kindly note that the GMAT® test is a registered trademark of the Graduate Management Admission Council®, and this site has neither been reviewed nor endorsed by GMAC®.