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

It is currently 26 May 2019, 12:57

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

Between 1980 and 1985, Pierre’s investment portfolio increas

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

Hide Tags

 
Manager
Manager
User avatar
Status: Never ever give up on yourself.Period.
Joined: 23 Aug 2012
Posts: 136
Location: India
Concentration: Finance, Human Resources
GMAT 1: 570 Q47 V21
GMAT 2: 690 Q50 V33
GPA: 3.5
WE: Information Technology (Investment Banking)
Between 1980 and 1985, Pierre’s investment portfolio increas  [#permalink]

Show Tags

New post 14 Jan 2013, 06:56
4
21
00:00
A
B
C
D
E

Difficulty:

  95% (hard)

Question Stats:

30% (02:58) correct 70% (02:41) wrong based on 564 sessions

HideShow timer Statistics

Between 1980 and 1985, Pierre’s investment portfolio increased in value by x%. Between 1985 and 1990, the portfolio increased in value by y%. Since 1990, the portfolio has decreased in value by z%. If x, y, and z are all positive integers, is the portfolio currently worth more than it was in 1980?

(1) x + y > z

(2) y − x > z

_________________
Don't give up on yourself ever. Period.
Beat it, no one wants to be defeated (My journey from 570 to 690) : http://gmatclub.com/forum/beat-it-no-one-wants-to-be-defeated-journey-570-to-149968.html
Most Helpful Expert Reply
Math Expert
User avatar
V
Joined: 02 Sep 2009
Posts: 55277
Re: Between 1980 and 1985, Pierre’s investment portfolio increas  [#permalink]

Show Tags

New post 14 Jan 2013, 07:39
3
6
Between 1980 and 1985, Pierre’s investment portfolio increased in value by x%. Between 1985 and 1990, the portfolio increased in value by y%. Since 1990, the portfolio has decreased in value by z%. If x, y, and z are all positive integers, is the portfolio currently worth more than it was in 1980?

Say the value of the portfolio in 1980 was $1. then:

Price in 1980 = 1;
Price in 1985 = \((1+\frac{x}{100})\);
Price in 1990 = \((1+\frac{x}{100})(1+\frac{y}{100})\);
Price in now = \((1+\frac{x}{100})(1+\frac{y}{100})(1-\frac{z}{100})\).

Question asks whether \(1<(1+\frac{x}{100})(1+\frac{y}{100})(1-\frac{z}{100})\).

(1) x + y > z. If \(x=1\), \(y=100\), and \(z=1\), then \((1+\frac{x}{100})(1+\frac{y}{100})(1-\frac{z}{100})=1.01*2*0.99>1\) BUT if \(x=1\), \(y=100\), and \(z=90\), then \((1+\frac{x}{100})(1+\frac{y}{100})(1-\frac{z}{100})=1.01*2*0.1<1\). Not sufficient.

(2) y − x > z. Consider the same cases. Not sufficient.

(1)+(2) Consider the same cases. Not sufficient.

Answer: E.
_________________
General Discussion
Intern
Intern
User avatar
Joined: 27 Mar 2013
Posts: 4
GMAT 1: 480 Q32 V23
Re: Between 1980 and 1985, Pierre’s investment portfolio increas  [#permalink]

Show Tags

New post 01 Jun 2013, 09:33
can someone explain me the difference in reasoning between the question above and this question?:

gmatclub. com/forum/the-annual-rent-collected-by-a-corporation-from-a-certain-89184.html

the look similar, but the questions meant to be different:

The annual rent collected by a corporation from a certain building was x percent more in 1998 than in 1997 and y percent less in 1999 than in 1998. Was the annual rent collected by the corporation from the building more in 1999 than in 1997?

(1) x > y
(2) xy/100 < x-y


cant we make the reasoning there the same as here, r=1 and solve similiar as above?
VP
VP
User avatar
Status: Far, far away!
Joined: 02 Sep 2012
Posts: 1051
Location: Italy
Concentration: Finance, Entrepreneurship
GPA: 3.8
GMAT ToolKit User
Re: Between 1980 and 1985, Pierre’s investment portfolio increas  [#permalink]

Show Tags

New post 01 Jun 2013, 11:20
Kyuss wrote:
can someone explain me the difference in reasoning between the question above and this question?:

gmatclub. com/forum/the-annual-rent-collected-by-a-corporation-from-a-certain-89184.html

the look similar, but the questions meant to be different:

The annual rent collected by a corporation from a certain building was x percent more in 1998 than in 1997 and y percent less in 1999 than in 1998. Was the annual rent collected by the corporation from the building more in 1999 than in 1997?

(1) x > y
(2) xy/100 < x-y


cant we make the reasoning there the same as here, r=1 and solve similiar as above?


Yes you can. But whatever value of r you pick will eventually not matter.

I will go directly to the solution here, so we can write the question as:
\(R(1+\frac{x}{100})(1-\frac{y}{100})>R\), as you see now we can safely divide by R (which is positive) and obtain
\((1+\frac{x}{100})(1-\frac{y}{100})>1\). So you can assume \(R=1\) at the beginning if this makes your calculus easier.

Hope it's clear
_________________
It is beyond a doubt that all our knowledge that begins with experience.
Kant , Critique of Pure Reason

Tips and tricks: Inequalities , Mixture | Review: MGMAT workshop
Strategy: SmartGMAT v1.0 | Questions: Verbal challenge SC I-II- CR New SC set out !! , My Quant

Rules for Posting in the Verbal Forum - Rules for Posting in the Quant Forum[/size][/color][/b]
Intern
Intern
avatar
Joined: 19 Apr 2012
Posts: 23
Re: Between 1980 and 1985, Pierre’s investment portfolio increas  [#permalink]

Show Tags

New post 02 Jun 2013, 05:14
1
My approach:

Simple pick-numbers.

Origin value of the investment portfolio: 100. Increase by 10% and then also by 10% = 100*1,1 = 110
110 * 1,1 = 121. Decrease by 19% ~ 20% = 1/5 = ~ 24 so the total value is below 100.

Same approach for the second statement.

Clearly E.
Intern
Intern
avatar
Joined: 21 Mar 2013
Posts: 38
GMAT Date: 03-20-2014
GMAT ToolKit User
Re: Between 1980 and 1985, Pierre’s investment portfolio increas  [#permalink]

Show Tags

New post 18 Mar 2014, 03:43
Bunuel wrote:
(1) x + y > z. If \(x=1\), \(y=100\), and \(z=1\), then \((1+\frac{x}{100})(1+\frac{y}{100})(1-\frac{z}{100})=1.01*2*0.99>1\) BUT if \(x=1\), \(y=100\), and \(z=90\), then \((1+\frac{x}{100})(1+\frac{y}{100})(1-\frac{z}{100})=1.01*2*0.1<1\). Not sufficient.

(2) y − x > z. Consider the same cases. Not sufficient.

(1)+(2) Consider the same cases. Not sufficient.



Bunuel: Can you please share some thought on how to come up with such numbers for plugging in.
Manager
Manager
avatar
Joined: 20 Dec 2013
Posts: 226
Location: India
Re: Between 1980 and 1985, Pierre’s investment portfolio increas  [#permalink]

Show Tags

New post 30 Mar 2014, 01:00
Bunuel wrote:
Between 1980 and 1985, Pierre’s investment portfolio increased in value by x%. Between 1985 and 1990, the portfolio increased in value by y%. Since 1990, the portfolio has decreased in value by z%. If x, y, and z are all positive integers, is the portfolio currently worth more than it was in 1980?

Say the value of the portfolio in 1980 was $1. then:

Price in 1980 = 1;
Price in 1985 = \((1+\frac{x}{100})\);
Price in 1990 = \((1+\frac{x}{100})(1+\frac{y}{100})\);
Price in now = \((1+\frac{x}{100})(1+\frac{y}{100})(1-\frac{z}{100})\).

Question asks whether \(1<(1+\frac{x}{100})(1+\frac{y}{100})(1-\frac{z}{100})\).

(1) x + y > z. If \(x=1\), \(y=100\), and \(z=1\), then \((1+\frac{x}{100})(1+\frac{y}{100})(1-\frac{z}{100})=1.01*2*0.99>1\) BUT if \(x=1\), \(y=100\), and \(z=90\), then \((1+\frac{x}{100})(1+\frac{y}{100})(1-\frac{z}{100})=1.01*2*0.1<1\). Not sufficient.

(2) y − x > z. Consider the same cases. Not sufficient.

(1)+(2) Consider the same cases. Not sufficient.

Answer: E.


I just want to know how you come up with these numbers,Bunuel?Is there any rule of thumb?
Intern
Intern
avatar
Joined: 01 Jun 2014
Posts: 5
Re: Between 1980 and 1985, Pierre’s investment portfolio increas  [#permalink]

Show Tags

New post 04 Jun 2014, 19:22
1
E. Pick the most extreme values of z: z = 1 and z = 100.

If z = 1, pick pretty much any large values of x and y to satisfy both statements 1 and 2, and you'll see that the portfolio has net grown.

If z = 100, then pick any large values of x and y to satisfy both statements 1 and 2, and the portfolio has become 0.

Both cases satisfy statements 1 and 2, but differ in the overall result. Therefore E.
Manager
Manager
User avatar
Joined: 14 Apr 2014
Posts: 60
Between 1980 and 1985, Pierre’s investment portfolio increas  [#permalink]

Show Tags

New post 25 Oct 2014, 04:37
Bunuel wrote:
Between 1980 and 1985, Pierre’s investment portfolio increased in value by x%. Between 1985 and 1990, the portfolio increased in value by y%. Since 1990, the portfolio has decreased in value by z%. If x, y, and z are all positive integers, is the portfolio currently worth more than it was in 1980?

Say the value of the portfolio in 1980 was $1. then:

Price in 1980 = 1;
Price in 1985 = \((1+\frac{x}{100})\);
Price in 1990 = \((1+\frac{x}{100})(1+\frac{y}{100})\);
Price in now = \((1+\frac{x}{100})(1+\frac{y}{100})(1-\frac{z}{100})\).

Question asks whether \(1<(1+\frac{x}{100})(1+\frac{y}{100})(1-\frac{z}{100})\).

(1) x + y > z. If \(x=1\), \(y=100\), and \(z=1\), then \((1+\frac{x}{100})(1+\frac{y}{100})(1-\frac{z}{100})=1.01*2*0.99>1\) BUT if \(x=1\), \(y=100\), and \(z=90\), then \((1+\frac{x}{100})(1+\frac{y}{100})(1-\frac{z}{100})=1.01*2*0.1<1\). Not sufficient.

(2) y − x > z. Consider the same cases. Not sufficient.

(1)+(2) Consider the same cases. Not sufficient.

Answer: E.


Can you please tell how did you choose these numbers ? I mean within two minutes finding these number may be little difficult. So is there are some number which I have to always take care of. Please help !
Manager
Manager
User avatar
S
Joined: 22 Jan 2014
Posts: 173
WE: Project Management (Computer Hardware)
Re: Between 1980 and 1985, Pierre’s investment portfolio increas  [#permalink]

Show Tags

New post 25 Oct 2014, 05:09
0
daviesj wrote:
Between 1980 and 1985, Pierre’s investment portfolio increased in value by x%. Between 1985 and 1990, the portfolio increased in value by y%. Since 1990, the portfolio has decreased in value by z%. If x, y, and z are all positive integers, is the portfolio currently worth more than it was in 1980?

(1) x + y > z

(2) y − x > z


E.

The quickest way to do this ques is by plugging in values for x,y,and z

1) x+y > z
Now looking at FS1 we can easily say that the portfolio value would easily be greater than that it was in 1980 (assuming x and y to be very large numbers and z to be really small)
To make the value smaller, we need negative growth...for that x,y,and z should be as close as possible.
let x=y=z=1
compound % growth in first 2 periods = 1+1+(1*1/100) = 2.01
compound % growth in 3rd period = 2.01 - 1 - .201 = .809 which is negative growth.
so insufficient.

2) y-x > z
Again positive growth can be show by assuming x and y to be large and z to be small
for negative growth: x=1, y=100, and z=98

(1)+(2) --> same can be done here.
_________________
Illegitimi non carborundum.
Intern
Intern
User avatar
B
Joined: 02 Jan 2019
Posts: 23
Re: Between 1980 and 1985, Pierre’s investment portfolio increas  [#permalink]

Show Tags

New post 11 Feb 2019, 10:19
Evaluate Statement (1), which states that x + y > z. Plug In values that satisfy this statement and determine the answer to the question. Plug In a starting portfolio value of $200 and values of x = 50, y = 50, and z = 10. These values satisfy Statement (1), because 50 + 50 > 10. Using these numbers the value of the portfolio would first increase 50% to $300, then increase another 50% to $450, then decrease by 10% to $405. Since $405 is greater than $200 the portfolio would be more than it was in 1980. The answer to the question is "Yes". Now Plug In different values to try to get an answer of "No." Plug In a starting portfolio value of $200 and values of x = 100, y = 100, and z = 100. These values satisfy Statement (1), because 100 + 100 > 100. The portfolio would first increase 100% to $400, then increase another 100% to $800, then decrease by 100% to have a final value of $0. Since $0 is less than $200 the portfolio would be worth less than it was in 1980. Now, the answer to the question is "No". When different numbers that satisfy a statement yield different answers to the question, the statement is insufficient. Write down BCE.

Now, evaluate Statement (2), which states that y − x > z. Plug In values that satisfy this statement and determine the answer to the question. Plug In a starting portfolio value of $200 and values of x = 10, y = 50, and z = 10. These values satisfy Statement (2), because 50 – 10 > 10. Using these numbers the value of the portfolio would first increase 10% to $220, then increase another 50% to $330, then decrease by 10% to $297. Since $297 is greater than $200 the portfolio would be worth more than it was in 1980. The answer to the question is "Yes". Now Plug In different values to try to get an answer of "No." Plug In a starting portfolio value of $200 and values of x = 10, y = 200, and z = 100. These values satisfy Statement (2), because 200 – 10 > 100. Using these values the portfolio would first increase 10% to $220, then increase another 200% to $660, then decrease by 100% to have a final value of $0. Since $0 is less than $200 the value of the portfolio is worth less than it was in 1980. The answer to the question is "No". When different numbers that satisfy a statement yield different answers to the question, the statement is insufficient. Eliminate B.

Now, evaluate Statement (1) and Statement (2) together. Plug In values that satisfy both of the statements at once and determine the answer to the question. The values used to evaluate Statement (2) also satisfy Statement (1), so both answers "Yes" and "No" are possible. Therefore, Statements (1) and (2) together are insufficient. Eliminate C.

The correct answer is choice E.
_________________
_________________
Regards
K Shrikanth

____________
Please appreciate the efforts by pressing +1 KUDOS (:
Intern
Intern
avatar
B
Joined: 13 Jun 2018
Posts: 37
GMAT 1: 700 Q49 V36
Re: Between 1980 and 1985, Pierre’s investment portfolio increas  [#permalink]

Show Tags

New post 15 Feb 2019, 12:04
Bunuel wrote:
Between 1980 and 1985, Pierre’s investment portfolio increased in value by x%. Between 1985 and 1990, the portfolio increased in value by y%. Since 1990, the portfolio has decreased in value by z%. If x, y, and z are all positive integers, is the portfolio currently worth more than it was in 1980?

Say the value of the portfolio in 1980 was $1. then:

Price in 1980 = 1;
Price in 1985 = \((1+\frac{x}{100})\);
Price in 1990 = \((1+\frac{x}{100})(1+\frac{y}{100})\);
Price in now = \((1+\frac{x}{100})(1+\frac{y}{100})(1-\frac{z}{100})\).

Question asks whether \(1<(1+\frac{x}{100})(1+\frac{y}{100})(1-\frac{z}{100})\).

(1) x + y > z. If \(x=1\), \(y=100\), and \(z=1\), then \((1+\frac{x}{100})(1+\frac{y}{100})(1-\frac{z}{100})=1.01*2*0.99>1\) BUT if \(x=1\), \(y=100\), and \(z=90\), then \((1+\frac{x}{100})(1+\frac{y}{100})(1-\frac{z}{100})=1.01*2*0.1<1\). Not sufficient.

(2) y − x > z. Consider the same cases. Not sufficient.

(1)+(2) Consider the same cases. Not sufficient.

Answer: E.


Can you please elaborate on the (1)+(2) case Bunuel?

Thank you!
Intern
Intern
User avatar
B
Joined: 02 Jan 2019
Posts: 23
Re: Between 1980 and 1985, Pierre’s investment portfolio increas  [#permalink]

Show Tags

New post 16 Feb 2019, 05:34
Bunuel wrote:
Between 1980 and 1985, Pierre’s investment portfolio increased in value by x%. Between 1985 and 1990, the portfolio increased in value by y%. Since 1990, the portfolio has decreased in value by z%. If x, y, and z are all positive integers, is the portfolio currently worth more than it was in 1980?

Say the value of the portfolio in 1980 was $1. then:

Price in 1980 = 1;
Price in 1985 = \((1+\frac{x}{100})\);
Price in 1990 = \((1+\frac{x}{100})(1+\frac{y}{100})\);
Price in now = \((1+\frac{x}{100})(1+\frac{y}{100})(1-\frac{z}{100})\).

Question asks whether \(1<(1+\frac{x}{100})(1+\frac{y}{100})(1-\frac{z}{100})\).

(1) x + y > z. If \(x=1\), \(y=100\), and \(z=1\), then \((1+\frac{x}{100})(1+\frac{y}{100})(1-\frac{z}{100})=1.01*2*0.99>1\) BUT if \(x=1\), \(y=100\), and \(z=90\), then \((1+\frac{x}{100})(1+\frac{y}{100})(1-\frac{z}{100})=1.01*2*0.1<1\). Not sufficient.

(2) y − x > z. Consider the same cases. Not sufficient.

(1)+(2) Consider the same cases. Not sufficient.

Answer: E.


Hi
Even for C (1 & 2 combined),
We need to consider values of X, Y & Z that need to satisfy both the cases.
In case of bunuel's example, he has considered \(x=1\), \(y=100\), and \(z=1\). which satisfy both 1 & 2.
And as we have seen in case 1 that eqn. \((1+\frac{x}{100})(1+\frac{y}{100})(1-\frac{z}{100})\)can be both less than or greater than 1.

If \(x=1\), \(y=100\), and \(z=1\), then \((1+\frac{x}{100})(1+\frac{y}{100})(1-\frac{z}{100})=1.01*2*0.99>1\) BUT if \(x=1\), \(y=100\), and \(z=90\), then \((1+\frac{x}{100})(1+\frac{y}{100})(1-\frac{z}{100})=1.01*2*0.1<1\).

So in case of C too the answer is Not sufficient.
_________________
_________________
Regards
K Shrikanth

____________
Please appreciate the efforts by pressing +1 KUDOS (:
GMAT Club Bot
Re: Between 1980 and 1985, Pierre’s investment portfolio increas   [#permalink] 16 Feb 2019, 05:34
Display posts from previous: Sort by

Between 1980 and 1985, Pierre’s investment portfolio increas

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


cron
Copyright

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®.