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

Redeem

If a/b > 4, is a > 8?

This topic has expert replies
Post new topic Post Reply
Previous Topic Next Topic
Source: — Data Sufficiency |

GMAT/MBA Expert

User avatar
GMAT Instructor
Posts: 3008
Joined: Mon Aug 22, 2016 6:19 am
Location: Grand Central / New York
Thanked: 470 times
Followed by:34 members

by Jay@ManhattanReview » Mon Jan 07, 2019 12:06 am

Timer

00:00

Your Answer

A

B

C

D

E

Global Stats

VJesus12 wrote:If a/b > 4, is a > 8?

(1) b > 2
(2) a > 7

[spoiler]OA=A[/spoiler]

Source: Princeton Review
Given: a/b > 4

We have to determine whether a > 8.

Let's take each statement one by one.

(1) b > 2

Given b > 2 means that b is positive, thus, we can multiply b to both the sides of a/b > 4.

Thus, we have a/b > 4 => (a/b)*b > 4*b => a > 4b. Say b = 2.001, then a > 4*2.001 => a > 8. Suiificient.

(2) a > 7

Case 1: Say a = 7.5 < 8. Thus, from a/b > 4, we have 7.5/b > 4 => 7.5/4 > b. Since b can have any value, it is a valid case. The answer is No.
Case 2: Say a = 10. Thus, from a/b > 4, we have 10/b > 4 => 10/4 > b. Since b can have any value, it is a valid case. The answer is Yes.

No unique answer. Insufficient.

The correct answer: A

Hope this helps!

-Jay
_________________
Manhattan Review

Locations: Manhattan Review Malleswaram | GMAT Prep Vijayawada | GRE Prep Mumbai | New Delhi GRE Coaching | and many more...

Schedule your free consultation with an experienced GMAT Prep Advisor! Click here.
Top
User avatar
GMAT Instructor
Posts: 1449
Joined: Sat Oct 09, 2010 2:16 pm
Thanked: 59 times
Followed by:33 members

by fskilnik@GMATH » Mon Jan 07, 2019 3:40 am

Timer

00:00

Your Answer

A

B

C

D

E

Global Stats

VJesus12 wrote:If a/b > 4, is a > 8?

(1) b > 2
(2) a > 7
Source: Princeton Review
$${a \over b} > 4$$
$$a\,\,\mathop > \limits^? \,\,8$$
$$\left( 1 \right)\,\,\,\left\{ \matrix{
\,b > 2 \hfill \cr
\,{a \over b} > 4 \hfill \cr} \right.\,\,\,\,\,\,\, \Rightarrow \,\,\,\,\,a\,\,\, = \,\,\,b \cdot {a \over b}\,\,\, > \,\,\,2 \cdot 4\,\,\, = \,\,\,8\,\,\,\,\,\,\, \Rightarrow \,\,\,\,{\rm{SUFF}}.\,\,$$
$$\left( 2 \right)\,\,a > 7\,\,\,\left\{ \matrix{
\,{\rm{Take}}\,\,\left( {a,b} \right) = \left( {8,1} \right)\,\,\,\, \Rightarrow \,\,\,\left\langle {{\rm{NO}}} \right\rangle \,\, \hfill \cr
\,{\rm{Take}}\,\,\left( {a,b} \right) = \left( {9,1} \right)\,\,\,\, \Rightarrow \,\,\,\left\langle {{\rm{YES}}} \right\rangle \,\, \hfill \cr} \right.$$


This solution follows the notations and rationale taught in the GMATH method.

Regards,
Fabio.
Fabio Skilnik :: GMATH method creator ( Math for the GMAT)
English-speakers :: https://www.gmath.net
Portuguese-speakers :: https://www.gmath.com.br
Top
Post new topic Post Reply
• Page 1 of 1