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

 It is currently 23 Jun 2018, 20:25

### 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 a^2=b, is the value of a between 0 and 1?

Author Message
TAGS:

### Hide Tags

Intern
Joined: 22 Oct 2012
Posts: 7
If a^2=b, is the value of a between 0 and 1? [#permalink]

### Show Tags

Updated on: 01 Dec 2012, 05:59
1
3
00:00

Difficulty:

85% (hard)

Question Stats:

39% (01:08) correct 61% (01:12) wrong based on 189 sessions

### HideShow timer Statistics

If a^2=b, is the value of a between 0 and 1?

(1) b is between 0 and 1
(2) a>b

Originally posted by cv3t3l1na on 01 Dec 2012, 00:37.
Last edited by Bunuel on 01 Dec 2012, 05:59, edited 1 time in total.
Edited the question.
Senior Manager
Joined: 22 Dec 2011
Posts: 271
Re: If a*a=b, is the value of a between 0 and 1? [#permalink]

### Show Tags

Updated on: 01 Dec 2012, 07:23
cv3t3l1na wrote:
If a*a=b, is the value of a between 0 and 1?
1. b is between 0 and 1
2. a>b

Why 2. is not sufficient?

Huh? Inside the spoiler you have given OA as B?

I guess both a sufficient by itself to answer to question "is the value of a between 0 and 1?"

Question rephrase ->$$a*a = b ; a^2 = b ; a = +/- \sqrt{b}$$
Is $$0 < a < 1$$

Stat1/Given B is between 0 and 1.
a= 0.5 then b = 0.25 ; a is in between 0 and 1
a = -0.5 then b = 0.25 ; a is NOT between 0 and 1.
InSufficient

Stat2/ If $$a > b & a =\sqrt{b}$$only values that would satisfy these equations would be value from 0 to 1. Sufficient.

So D it is....

Cheers

Originally posted by Jp27 on 01 Dec 2012, 04:15.
Last edited by Jp27 on 01 Dec 2012, 07:23, edited 2 times in total.
VP
Joined: 02 Jul 2012
Posts: 1194
Location: India
Concentration: Strategy
GMAT 1: 740 Q49 V42
GPA: 3.8
WE: Engineering (Energy and Utilities)
Re: If a*a=b, is the value of a between 0 and 1? [#permalink]

### Show Tags

01 Dec 2012, 06:18
Jp27 wrote:
cv3t3l1na wrote:
If a*a=b, is the value of a between 0 and 1?
1. b is between 0 and 1
2. a>b

Why 2. is not sufficient?

Huh? Inside the spoiler you have given OA as B?

I guess both a sufficient by itself to answer to question "is the value of a between 0 and 1?"

Question rephrase ->$$a*a = b ; a^2 = b ; a = \sqrt{b}$$
Is $$0 < a < 1$$

Stat1/ If B is between 0 and 1. Root of any value between 0 and 1 will result in a value larger than B but will still be fraction between 0 and 1. Sufficient

Stat2/ If $$a > b & a =\sqrt{b}$$only values that would satisfy these equations would be value from 0 to 1. Sufficient.

So D it is....

Cheers

If a = -0.5, b =0.25
a = 0.5 , b = 0.25 ...
_________________

Did you find this post helpful?... Please let me know through the Kudos button.

Thanks To The Almighty - My GMAT Debrief

GMAT Reading Comprehension: 7 Most Common Passage Types

Senior Manager
Joined: 22 Dec 2011
Posts: 271
Re: If a*a=b, is the value of a between 0 and 1? [#permalink]

### Show Tags

01 Dec 2012, 06:45
MacFauz wrote:
Jp27 wrote:
cv3t3l1na wrote:
If a*a=b, is the value of a between 0 and 1?
1. b is between 0 and 1
2. a>b

Why 2. is not sufficient?

Huh? Inside the spoiler you have given OA as B?

I guess both a sufficient by itself to answer to question "is the value of a between 0 and 1?"

Question rephrase ->$$a*a = b ; a^2 = b ; a = \sqrt{b}$$
Is $$0 < a < 1$$

Stat1/ If B is between 0 and 1. Root of any value between 0 and 1 will result in a value larger than B but will still be fraction between 0 and 1. Sufficient

Stat2/ If $$a > b & a =\sqrt{b}$$only values that would satisfy these equations would be value from 0 to 1. Sufficient.

So D it is....

Cheers

If a = -0.5, b =0.25
a = 0.5 , b = 0.25 ...

I will edit my response...!
Math Expert
Joined: 02 Sep 2009
Posts: 46297
Re: If a^2=b, is the value of a between 0 and 1? [#permalink]

### Show Tags

01 Dec 2012, 06:54
1
If a^2=b, is the value of a between 0 and 1?

$$a^2=b$$ --> $$a=-\sqrt{b}$$ or $$a=\sqrt{b}$$.

(1) b is between 0 and 1. If $$b=\frac{1}{4}$$, then $$a$$ could be $$-\frac{1}{2}$$ (answer NO) or $$\frac{1}{2}$$ (answer YES). Not sufficient.

(2) a>b --> $$a=\sqrt{b}$$ --> $$0<b<1$$. Sufficient.

_________________
Intern
Joined: 10 Apr 2013
Posts: 13
Location: United States (TX)
Concentration: Finance, Entrepreneurship
GMAT 1: 740 Q50 V41
GPA: 3.3
WE: Analyst (Investment Banking)
Re: If a^2=b, is the value of a between 0 and 1? [#permalink]

### Show Tags

02 Sep 2015, 10:02
cv3t3l1na wrote:
If a^2=b, is the value of a between 0 and 1?

(1) b is between 0 and 1
(2) a>b

This graph helped me understand this question:

You can clearly see b as the red diagonal and a^{2} as the blue curve

(1) b is between 0 and 1
You can see that where the red line is between 0 and 1, the blue curve is between -1 and 1

(2) a > b
You can see the only portion of the graph where the red line is above the blue curve is between 0 and 1
Math Revolution GMAT Instructor
Joined: 16 Aug 2015
Posts: 5600
GMAT 1: 800 Q59 V59
GPA: 3.82
If a^2=b, is the value of a between 0 and 1? [#permalink]

### Show Tags

03 Sep 2015, 04:49
1
Forget conventional ways of solving math questions. In DS, Variable approach is the easiest and quickest way to find the answer without actually solving the problem. Remember equal number of variables and equations ensures a solution.

If a^2=b, is the value of a between 0 and 1?

(1) b is between 0 and 1
(2) a>b

There is nothing to transform in the original condition and the question. WE have 2 variable (a,b) and 1 equation (a^2=b), thus we need 1 more to match the number of variables and equations. Since there is 1 each in 1) and 2), D is likely the answer.

In case of 1), if b=0.04 then the answer is no if a=-0.2 and yes if a=0.2 Thus it is not sufficient.
In case of 2), a>b=a^2, a>a^2, 0>a^2-a, 0>a(a-1), 0<a<1, therefore the answer is yes.
_________________

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"

Senior Manager
Joined: 06 Jul 2016
Posts: 421
Location: Singapore
Concentration: Strategy, Finance
Re: If a^2=b, is the value of a between 0 and 1? [#permalink]

### Show Tags

03 Aug 2017, 12:50
cv3t3l1na wrote:
If a^2=b, is the value of a between 0 and 1?

(1) b is between 0 and 1
(2) a>b

Is 1>a>0 ?

1) 1>b>0
$$a^2$$ = b
a > 0 or a < 0
a = $$\frac{1}{2}$$ , b = $$\frac{1}{4}$$ Yes
a = $$\frac{-1}{2}$$ , b = $$\frac{1}{4}$$ No
Insufficient.

2) a>b
This basically means a cannot be less than 0.
and since $$a^2$$ = b
=> a > $$a^2$$
=> 1>a>0
B is sufficient.
_________________

Put in the work, and that dream score is yours!

Re: If a^2=b, is the value of a between 0 and 1?   [#permalink] 03 Aug 2017, 12:50
Display posts from previous: Sort by