GMAT Changed on April 16th - Read about the latest changes here

 It is currently 21 May 2018, 20:54

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

Events & Promotions

Events & Promotions in June
Open Detailed Calendar

If 2a^2 + 0.5a - 1 = 0, then a(4a + 1) =

Author Message
TAGS:

Hide Tags

Math Expert
Joined: 02 Sep 2009
Posts: 45222
If 2a^2 + 0.5a - 1 = 0, then a(4a + 1) = [#permalink]

Show Tags

05 Sep 2017, 01:27
00:00

Difficulty:

15% (low)

Question Stats:

84% (01:18) correct 16% (02:09) wrong based on 54 sessions

HideShow timer Statistics

If $$2a^2 + 0.5a - 1 = 0$$, then $$a(4a + 1) =$$

A. 0.5
B. 2
C. 3.5
D. 4
E. 0

_________________
BSchool Forum Moderator
Joined: 26 Feb 2016
Posts: 2551
Location: India
GPA: 3.12
If 2a^2 + 0.5a - 1 = 0, then a(4a + 1) = [#permalink]

Show Tags

05 Sep 2017, 01:30
We have been asked to find the value for $$a(4a + 1) = 4a^2 + a$$.

$$2a^2 + 0.5a - 1 = 0$$ when multiplied by 2, gives $$4a^2 + a - 2 = 0$$
Hence, the expression $$4a^2 + a - 2 = 0$$ can be re-written as $$4a^2 + a = 2$$(Option B)
_________________

You've got what it takes, but it will take everything you've got

Manager
Joined: 27 Dec 2016
Posts: 232
Concentration: Social Entrepreneurship, Nonprofit
GPA: 3.65
WE: Sales (Consumer Products)
Re: If 2a^2 + 0.5a - 1 = 0, then a(4a + 1) = [#permalink]

Show Tags

05 Sep 2017, 01:31
Bunuel wrote:
If $$2a^2 + 0.5a - 1 = 0$$, then $$a(4a + 1) =$$

A. 0.5
B. 2
C. 3.5
D. 4
E. 0

- $$2a^2 +0.5a - 1 = 0$$, we can get rid of decimal by multiply by 2 -> $$4a^2 + a - 2 = 0$$.
- We can add both sides with 2 -> $$4a^2 + a = 2$$ -> $$4a^2 + a = -2$$ -> $$a(4a+1) = 2$$.

B.
_________________

There's an app for that - Steve Jobs.

Target Test Prep Representative
Status: Founder & CEO
Affiliations: Target Test Prep
Joined: 14 Oct 2015
Posts: 2597
Location: United States (CA)
Re: If 2a^2 + 0.5a - 1 = 0, then a(4a + 1) = [#permalink]

Show Tags

07 Sep 2017, 16:47
Bunuel wrote:
If $$2a^2 + 0.5a - 1 = 0$$, then $$a(4a + 1) =$$

A. 0.5
B. 2
C. 3.5
D. 4
E. 0

2a^2 + 0.5a - 1 = 0

4a^2 + a - 2 = 0

4a^2 + a = 2

a(4a + 1) = 2

_________________

Scott Woodbury-Stewart
Founder and CEO

GMAT Quant Self-Study Course
500+ lessons 3000+ practice problems 800+ HD solutions

Re: If 2a^2 + 0.5a - 1 = 0, then a(4a + 1) =   [#permalink] 07 Sep 2017, 16:47
Display posts from previous: Sort by