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

It is currently 16 Jul 2018, 07:07

Close

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
Your Progress

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.

Close

Request Expert Reply

Confirm Cancel

Is rst = 1 ? (1) r p t = s p t s (2) prt t = p t st

  new topic post reply Question banks Downloads My Bookmarks Reviews Important topics  
Author Message
TAGS:

Hide Tags

Expert Post
Math Expert
User avatar
V
Joined: 02 Sep 2009
Posts: 47015
Is rst = 1 ? (1) r p t = s p t s (2) prt t = p t st [#permalink]

Show Tags

New post 31 Dec 2017, 12:10
00:00
A
B
C
D
E

Difficulty:

  25% (medium)

Question Stats:

67% (00:54) correct 33% (01:01) wrong based on 69 sessions

HideShow timer Statistics

Expert Post
examPAL Representative
User avatar
S
Joined: 07 Dec 2017
Posts: 500
Re: Is rst = 1 ? (1) r p t = s p t s (2) prt t = p t st [#permalink]

Show Tags

New post 31 Dec 2017, 14:23
Bunuel wrote:
Is rst = 1 ?

(1) \(r\sqrt{t} =\frac{s\sqrt{t}}{s}\)


(2) \(\frac{rt}{\sqrt{t}}=\frac{\sqrt{t}}{st}\)


As this looks to be a very technical question (with many equations), we'll just solve it.
This is a Precise approach.

(1) We can cancel out \(s\) from the right-hand side giving \(r\sqrt{t} =\sqrt{t}\)
As we don't know if \(t = 0\) or not, we can't cancel it out but we can rewrite as \(r\sqrt{t} -\sqrt{t}=0\)
This simplifies to \(\sqrt{t}(r-1)=0\) meaning that \(t = 0\) or \(r = 1\).
Insufficient!

(2) Since both \(s\) and \(t\) are in the denominator, they can't be equal to 0 so we can multiply by them.
Multiplying by \(s\) and by \(\sqrt{t}\) gives \(rst = \frac{t}{t}=1\)
Sufficient!

(B) is our answer.
_________________

David
Senior tutor at examPAL
Signup for a free GMAT course
Image
We won some awards:
Image
Save up to $250 on examPAL packages (special for GMAT Club members)

Intern
Intern
avatar
B
Joined: 30 Oct 2017
Posts: 9
Re: Is rst = 1 ? (1) r p t = s p t s (2) prt t = p t st [#permalink]

Show Tags

New post 29 Jan 2018, 14:22
DavidTutorexamPAL wrote:
Bunuel wrote:
Is rst = 1 ?

(1) \(r\sqrt{t} =\frac{s\sqrt{t}}{s}\)


(2) \(\frac{rt}{\sqrt{t}}=\frac{\sqrt{t}}{st}\)


As this looks to be a very technical question (with many equations), we'll just solve it.
This is a Precise approach.

(1) We can cancel out \(s\) from the right-hand side giving \(r\sqrt{t} =\sqrt{t}\)
As we don't know if \(t = 0\) or not, we can't cancel it out but we can rewrite as \(r\sqrt{t} -\sqrt{t}=0\)
This simplifies to \(\sqrt{t}(r-1)=0\) meaning that \(t = 0\) or \(r = 1\).
Insufficient!

(2) Since both \(s\) and \(t\) are in the denominator, they can't be equal to 0 so we can multiply by them.
Multiplying by \(s\) and by \(\sqrt{t}\) gives \(rst = \frac{t}{t}=1\)
Sufficient!

(B) is our answer.



Can you please explain how you multiplied (2)? Cross multiply?

"2) Since both ss and tt are in the denominator, they can't be equal to 0 so we can multiply by them.
Multiplying by ss and by t√t gives rst=tt=1rst=tt=1
Sufficient!" I'm not seeing it, thanks.
Expert Post
Math Expert
User avatar
V
Joined: 02 Sep 2009
Posts: 47015
Re: Is rst = 1 ? (1) r p t = s p t s (2) prt t = p t st [#permalink]

Show Tags

New post 29 Jan 2018, 21:13
mekoner wrote:
DavidTutorexamPAL wrote:
Bunuel wrote:
Is rst = 1 ?

(1) \(r\sqrt{t} =\frac{s\sqrt{t}}{s}\)


(2) \(\frac{rt}{\sqrt{t}}=\frac{\sqrt{t}}{st}\)


As this looks to be a very technical question (with many equations), we'll just solve it.
This is a Precise approach.

(1) We can cancel out \(s\) from the right-hand side giving \(r\sqrt{t} =\sqrt{t}\)
As we don't know if \(t = 0\) or not, we can't cancel it out but we can rewrite as \(r\sqrt{t} -\sqrt{t}=0\)
This simplifies to \(\sqrt{t}(r-1)=0\) meaning that \(t = 0\) or \(r = 1\).
Insufficient!

(2) Since both \(s\) and \(t\) are in the denominator, they can't be equal to 0 so we can multiply by them.
Multiplying by \(s\) and by \(\sqrt{t}\) gives \(rst = \frac{t}{t}=1\)
Sufficient!

(B) is our answer.



Can you please explain how you multiplied (2)? Cross multiply?

"2) Since both ss and tt are in the denominator, they can't be equal to 0 so we can multiply by them.
Multiplying by ss and by t√t gives rst=tt=1rst=tt=1
Sufficient!" I'm not seeing it, thanks.


Yes, you can cross-multiply to get: rst^2 = t. Then reduce by t to get rst = 1.
_________________

New to the Math Forum?
Please read this: Ultimate GMAT Quantitative Megathread | All You Need for Quant | PLEASE READ AND FOLLOW: 12 Rules for Posting!!!

Resources:
GMAT Math Book | Triangles | Polygons | Coordinate Geometry | Factorials | Circles | Number Theory | Remainders; 8. Overlapping Sets | PDF of Math Book; 10. Remainders | GMAT Prep Software Analysis | SEVEN SAMURAI OF 2012 (BEST DISCUSSIONS) | Tricky questions from previous years.

Collection of Questions:
PS: 1. Tough and Tricky questions; 2. Hard questions; 3. Hard questions part 2; 4. Standard deviation; 5. Tough Problem Solving Questions With Solutions; 6. Probability and Combinations Questions With Solutions; 7 Tough and tricky exponents and roots questions; 8 12 Easy Pieces (or not?); 9 Bakers' Dozen; 10 Algebra set. ,11 Mixed Questions, 12 Fresh Meat

DS: 1. DS tough questions; 2. DS tough questions part 2; 3. DS tough questions part 3; 4. DS Standard deviation; 5. Inequalities; 6. 700+ GMAT Data Sufficiency Questions With Explanations; 7 Tough and tricky exponents and roots questions; 8 The Discreet Charm of the DS; 9 Devil's Dozen!!!; 10 Number Properties set., 11 New DS set.


What are GMAT Club Tests?
Extra-hard Quant Tests with Brilliant Analytics

Senior Manager
Senior Manager
avatar
G
Joined: 31 Jul 2017
Posts: 372
Location: Malaysia
WE: Consulting (Energy and Utilities)
Re: Is rst = 1 ? (1) r p t = s p t s (2) prt t = p t st [#permalink]

Show Tags

New post 01 Feb 2018, 01:24
Bunuel wrote:
Is rst = 1 ?

(1) \(r\sqrt{t} =\frac{s\sqrt{t}}{s}\)


(2) \(\frac{rt}{\sqrt{t}}=\frac{\sqrt{t}}{st}\)


Statement I:

\(\sqrt{t} (r-1) = 0\) ---> \(t = 0 , r = 1\)

Statement II:

\(r\sqrt{t} - 1/s\sqrt{t} = 0\)
\(rst = 1.\)

So, B.
_________________

If my Post helps you in Gaining Knowledge, Help me with KUDOS.. !!

Re: Is rst = 1 ? (1) r p t = s p t s (2) prt t = p t st   [#permalink] 01 Feb 2018, 01:24
Display posts from previous: Sort by

Is rst = 1 ? (1) r p t = s p t s (2) prt t = p t st

  new topic post reply Question banks Downloads My Bookmarks Reviews Important topics  

Events & Promotions

PREV
NEXT


GMAT Club MBA Forum Home| About| Terms and Conditions and Privacy Policy| GMAT Club Rules| Contact| Sitemap

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

Kindly note that the GMAT® test is a registered trademark of the Graduate Management Admission Council®, and this site has neither been reviewed nor endorsed by GMAC®.