 It is currently 26 Mar 2019, 04:16 ### 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

#### Not interested in getting valuable practice questions and articles delivered to your email? No problem, unsubscribe here. # a is directly proportional to b. If a = 8 when b = 2, what  Question banks Downloads My Bookmarks Reviews Important topics
Author Message
TAGS:
GRE Prep Club Legend  Joined: 07 Jun 2014
Posts: 4857
GRE 1: Q167 V156 WE: Business Development (Energy and Utilities)
Followers: 105

Kudos [?]: 1783 , given: 397

a is directly proportional to b. If a = 8 when b = 2, what [#permalink]
Expert's post 00:00

Question Stats: 90% (00:34) correct 9% (00:40) wrong based on 11 sessions
a is directly proportional to b. If a = 8 when b = 2, what is a when b = 4?

(A) 10
(B) 16
(C) 32
(D) 64
(E) 128
[Reveal] Spoiler: OA

_________________

Sandy
If you found this post useful, please let me know by pressing the Kudos Button

Try our free Online GRE Test Intern Joined: 16 Jul 2018
Posts: 4
Followers: 0

Kudos [?]: 5  , given: 0

Re: a is directly proportional to b. If a = 8 when b = 2, what [#permalink]
1
KUDOS
The question can be restated as ax=b, so subbing in a=8 and b=2, we solve 8x=2 for x, giving us x=1/4. We then solve for the new a value given by a*0.25=4 from which we get a=16. Manager  Joined: 06 Jun 2018
Posts: 94
Followers: 0

Kudos [?]: 58  , given: 0

Re: a is directly proportional to b. If a = 8 when b = 2, what [#permalink]
1
KUDOS
sandy wrote:
a is directly proportional to b. If a = 8 when b = 2, what is a when b = 4?

(A) 10
(B) 16
(C) 32
(D) 64
(E) 128

when b is 2, a is 8

when b is (2*2) =4, a is (8*2) = 16.

The best answer is B.
GRE Prep Club Legend  Joined: 07 Jun 2014
Posts: 4857
GRE 1: Q167 V156 WE: Business Development (Energy and Utilities)
Followers: 105

Kudos [?]: 1783 , given: 397

Re: a is directly proportional to b. If a = 8 when b = 2, what [#permalink]
Expert's post
Explanation

To answer this question, it is important to understand what is meant by the phrase “directly proportional.”

It means that $$a = kb$$, where k is a constant.

In alternative form: = k, where k is a constant.

So, because they both equal the constant, $$\frac{a_{old}}{b_{old}}=\frac{a_{new}}{b_{new}}$$. Plugging in values: $$\frac{8}{2}=\frac{a_{new}}{4}$$.
Crossmultiply and solve:
$$32 = 2a_{new}$$
$$a_{new} = 16$$
_________________

Sandy
If you found this post useful, please let me know by pressing the Kudos Button

Try our free Online GRE Test Re: a is directly proportional to b. If a = 8 when b = 2, what   [#permalink] 28 Jul 2018, 16:18
Display posts from previous: Sort by

# a is directly proportional to b. If a = 8 when b = 2, what  Question banks Downloads My Bookmarks Reviews Important topics 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®.