Last visit was: 22 Dec 2024, 15:40 It is currently 22 Dec 2024, 15:40

Close

GRE Prep 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
Your Progress

every week, we’ll send you an estimated GRE 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.

Close

Request Expert Reply

Confirm Cancel
User avatar
Director
Director
Joined: 22 Jun 2019
Posts: 521
Own Kudos [?]: 722 [4]
Given Kudos: 161
Send PM
Retired Moderator
Joined: 10 Apr 2015
Posts: 6218
Own Kudos [?]: 12234 [3]
Given Kudos: 136
Send PM
Verbal Expert
Joined: 18 Apr 2015
Posts: 30475
Own Kudos [?]: 36820 [0]
Given Kudos: 26100
Send PM
avatar
Manager
Manager
Joined: 22 May 2019
Posts: 58
Own Kudos [?]: 51 [2]
Given Kudos: 0
Send PM
Re: -1<a<0<|a|<b<1 [#permalink]
2
I am just curious, is that math mathematically valid? I might be terribly wrong. Even that, I wanna share my thought. As we know a must be negative. So in A, how could we validate the square root of something negative?


Thanks,
Verbal Expert
Joined: 18 Apr 2015
Posts: 30475
Own Kudos [?]: 36820 [0]
Given Kudos: 26100
Send PM
Re: -1<a<0<|a|<b<1 [#permalink]
Expert Reply
a is negative because is between -1 and zero.

Must be negative.

However, when it is inside the absolute value, it must be positive. After zero.

regards
Retired Moderator
Joined: 10 Apr 2015
Posts: 6218
Own Kudos [?]: 12234 [2]
Given Kudos: 136
Send PM
Re: -1<a<0<|a|<b<1 [#permalink]
2
AlaminMolla wrote:
I am just curious, is that math mathematically valid? I might be terribly wrong. Even that, I wanna share my thought. As we know a must be negative. So in A, how could we validate the square root of something negative?


Thanks,


You're absolutely correct. It's a bad question.
I didn't look closely inside the bracketed part, since it all gets squared in the end.
If a < 0, then √a is undefined, which renders the question invalid.
The GRE would never have a question like this.

Cheers,
Brent
User avatar
Director
Director
Joined: 22 Jun 2019
Posts: 521
Own Kudos [?]: 722 [0]
Given Kudos: 161
Send PM
Re: -1<a<0<|a|<b<1 [#permalink]
GreenlightTestPrep wrote:
AlaminMolla wrote:
I am just curious, is that math mathematically valid? I might be terribly wrong. Even that, I wanna share my thought. As we know a must be negative. So in A, how could we validate the square root of something negative?


Thanks,


You're absolutely correct. It's a bad question.
I didn't look closely inside the bracketed part, since it all gets squared in the end.
If a < 0, then √a is undefined, which renders the question invalid.
The GRE would never have a question like this.

Cheers,
Brent


:) :) :)
Intern
Intern
Joined: 02 Jan 2021
Posts: 27
Own Kudos [?]: 12 [1]
Given Kudos: 41
Send PM
-1<a<0<|a|<b<1 [#permalink]
1
Carcass GreenlightTestPrep

I got the answer as B in this way. I learnt comparison in this way from Kaplan. Is this valid?

given quantity A :

(a^2 *√b)^2 = (a^4 * b)\ a = a^3 b
___________
(√a)^2


given quantity b :

a * b^5
_______ = ( a * b^5) / b^2 = a * b^3
(√b)^4

comparing qty A and qty B

a^3 * b = a * b^3

simplifying by dividing both sides by ab we get

Qty A = a^2

Qty B = b ^2

we are given a range to pick values for a and b

so when I take a = -0.6 and Mod a = 0.6 which must be less than b. So I pick b = 0.8 and b must be less than 1.

now squaring a and b

I get Qty A = 0.36 and Qty B = 0.64

Now B is the answer isn't it?

Pls correct me if am wrong somewhere.
Verbal Expert
Joined: 18 Apr 2015
Posts: 30475
Own Kudos [?]: 36820 [0]
Given Kudos: 26100
Send PM
Re: -1<a<0<|a|<b<1 [#permalink]
Expert Reply
Hi

the answer is A and I suggest you to read very careful the GreenlightTestPrep explanation.

it is neat and marvelous.

Also read our book for better insights https://gre.myprepclub.com/forum/gre-math- ... -2609.html

Feel free to ask for further assistance

PS: I saw the one you posted method pretty cumbersome
Retired Moderator
Joined: 10 Apr 2015
Posts: 6218
Own Kudos [?]: 12234 [1]
Given Kudos: 136
Send PM
Re: -1<a<0<|a|<b<1 [#permalink]
1
This isn't a good question, and it won't help you prepare for the GRE.
Since \(a\) is negative, \(\sqrt{a}\) is not defined. In other words, it has no real value.

This means evaluating \(\left[ \begin{array}{cc|r} \frac{a^2 \sqrt{b}}{ \sqrt{a}} \end{array} \right]^2\) is similar to evaluating \(\left[ \begin{array}{cc|r} \frac{a^2 \sqrt{b}}{apple} \end{array} \right]^2\)
Senior Manager
Senior Manager
Joined: 23 Jan 2021
Posts: 294
Own Kudos [?]: 172 [0]
Given Kudos: 81
Concentration: , International Business
Send PM
Re: -1<a<0<|a|<b<1 [#permalink]
AjanthaJ wrote:
Carcass GreenlightTestPrep

I got the answer as B in this way. I learnt comparison in this way from Kaplan. Is this valid?

given quantity A :

(a^2 *√b)^2 = (a^4 * b)\ a = a^3 b
___________
(√a)^2


given quantity b :

a * b^5

_______ = ( a * b^5) / b^2 = a * b^3
(√b)^4

comparing qty A and qty B

a^3 * b = a * b^3

simplifying by dividing both sides by ab we get

Qty A = a^2

Qty B = b ^2

we are given a range to pick values for a and b

so when I take a = -0.6 and Mod a = 0.6 which must be less than b. So I pick b = 0.8 and b must be less than 1.

now squaring a and b

I get Qty A = 0.36 and Qty B = 0.64

Now B is the answer isn't it?

Pls correct me if am wrong somewhere.

Hi, i got the same as yours, but what i figure out in last is we cannot divide the quantity if it is negative. product of ab is clearly negative thats why we misscalculate the question.
Verbal Expert
Joined: 18 Apr 2015
Posts: 30475
Own Kudos [?]: 36820 [0]
Given Kudos: 26100
Send PM
Re: -1<a<0<|a|<b<1 [#permalink]
Expert Reply
Post locked

The discussion is located here https://gre.myprepclub.com/forum/1-a-0-a-b ... tml#p23077

Regards
Prep Club for GRE Bot
Re: -1<a<0<|a|<b<1 [#permalink]
Moderators:
Retired Moderator
6218 posts
Moderator
1115 posts
Retired Moderator
187 posts
Retired Moderator
348 posts
Retired Moderator
160 posts
GRE Instructor
117 posts
Retired Moderator
63 posts
Retired Moderator
1307 posts

Powered by phpBB © phpBB Group | Emoji artwork provided by EmojiOne