BREAKING: Target Test Prep releases Brand New 2026 On Demand GMAT prep course

Redeem

OG : DS : 79

This topic has expert replies
Post new topic Post Reply
Previous Topic Next Topic
User avatar
Senior | Next Rank: 100 Posts
Posts: 55
Joined: Tue Oct 13, 2009 6:08 pm
Location: NY
Thanked: 3 times

OG : DS : 79

by nasir » Sat Aug 28, 2010 12:08 am
Leo can buy a certain computer for P1 $ in state A, where the sales tax is t1 %, or he can buy the same computer for P2 $ in state B, where the sales tax is t2 %. is the total cost of the computer greater in state A than in state B ?

1- t1 > t2

2- P1.t1 > P2.t2


Why statement 2 alone is not sufficient ?
Top
Source: — Data Sufficiency |
User avatar
Master | Next Rank: 500 Posts
Posts: 164
Joined: Sun Jul 18, 2010 5:26 am
Thanked: 49 times
Followed by:4 members
GMAT Score:710

by Maciek » Sat Aug 28, 2010 9:29 am
statement 2 is INSUFFICIENT because we can't compare the costs

cost of the computer in the state A:

C1 = P1 $ - (t1 %)*(P1 $) = P1 $(1 - t1 %)

cost of the computer in the state B:

C2 = P2 $ - (t2 %)*(P2 $) = P2 $(1 - t2 %)

2- P1.t1 > P2.t2

C1 > C2 ?

P1 $(1 - t1 %) > P2 $(1 - t2 %) ?

we need more information about prices

hope it helps!

Best,
Maciek
"There is no greater wealth in a nation than that of being made up of learned citizens." Pope John Paul II

if you have any questions, send me a private message!

should you find this post useful, please click on "thanks" button :)
Top
User avatar
Legendary Member
Posts: 1309
Joined: Wed Mar 17, 2010 11:41 pm
Thanked: 33 times
Followed by:5 members

by pradeepkaushal9518 » Sat Aug 28, 2010 10:05 am
suppose p1=100 t1=10% so total cost = 100-10=90

p2=100 t2=5% so cost=100-5=95

1. t1>t2 but it doesnt tell about p1 n p2 so not suff

2.p1.t1>p2.t2 this also nt suff

combing we dont nething soE
A SMALL TOWN GUY
Top
Newbie | Next Rank: 10 Posts
Posts: 4
Joined: Tue Sep 28, 2010 4:56 pm
Location: Australia
GMAT Score:480

by All4GMAT » Tue Oct 26, 2010 6:12 pm
I have a solution which differs from the Official Guide answer - E. I think the question's answer is C, i.e. both statements together are sufficient to answer the question.

Question is if P1 + T1/100 (P1) > P2 + T2/100 (P2) ??

Solution:

From Statement 1 : T1 > T2
So, T1/100 > T2/100

So, 1 + T1/100 > 1 + T2/100

So, P1 (1 + T1/100) > P1 (1 + T2/100) -------------- I

From Statement 2 : P1T1 > P2T2

Dividing Statement 2 by Statement 1, we have

P1T1/T1 > P2T2/T2

So, P1 > P2 ------------------------------------------------ II

From Statement I and II,

P1 (1 + T1/100) > P2 (1 + T2/100)

Thus, P1 + T1/100 (P1) > P2 + T2/100 (P2)

Shouldn't the answer be C?

Please correct me if I am wrong guys??
Top
User avatar
GMAT Instructor
Posts: 1449
Joined: Sat Oct 09, 2010 2:16 pm
Thanked: 59 times
Followed by:33 members

by fskilnik@GMATH » Wed Oct 27, 2010 3:13 am
All4GMAT wrote:From Statement 1 : T1 > T2

From Statement 2 : P1T1 > P2T2

Dividing Statement 2 by Statement 1, we have

P1T1/T1 > P2T2/T2
Please correct me if I am wrong guys??
This is your mistake, All4GMAT !!

You CANNOT divide inequalities!

Example: 2 > 1 and 5 > 2 but 2/5 > 1/2 is wrong...


Another important thing: the difference between your "mathematization" of the question stem and the others: you think that the tax is put OVER the price, the others believe the price INCLUDES the tax.... I guess it´s a matter of the country you live on, because here in Brazil "your" approach would be more natural, but I BELIEVE that in USA it is the other way round, therefore I guess you should use Maciek´s structure (very well explained!) for the GMAT, but it seems to me that the question itself relates to the TOTAL COST and therefore, it seems to me, that this concept should be translated by "P1 > P2 ?"
Fabio Skilnik :: GMATH method creator ( Math for the GMAT)
English-speakers :: https://www.gmath.net
Portuguese-speakers :: https://www.gmath.com.br
Top
User avatar
GMAT Instructor
Posts: 1449
Joined: Sat Oct 09, 2010 2:16 pm
Thanked: 59 times
Followed by:33 members

by fskilnik@GMATH » Wed Oct 27, 2010 3:35 am
nasir wrote:Leo can buy a certain computer for P1 $ in state A, where the sales tax is t1 %, or he can buy the same computer for P2 $ in state B, where the sales tax is t2 %. is the total cost of the computer greater in state A than in state B ?

1- t1 > t2

2- P1.t1 > P2.t2
I suggest the following solution:

pre-tax amount in state A = p1 (1 - t1/100)
pre-tax amount in state B = p2 (1 - t2/100)

--------------------------------------------
Focus in the question: p1 > p2 ?
--------------------------------------------

(1) BIFURCATES (therefore is insufficient):

> Take t1 = 20, t2 = 10 and p1 = p2 = 100, that answers in the negative ;
> Take t1 = 20, t2 = 10 and p1 = 100, p2 = 90, that answers in the positive ;


(2) BIFURCATES (therefore insufficient):

> Take p1 = 100 , t1 = 20 (p1.t1 = 2,000) and p2 = 90 , t2 = 15 (p2.t2 = 900+450 = 1,350) answering in the positive;
> Take p1 = 80 , t1 = 20 (p1.t1 = 1,600) and p2 = 90 , t2 = 15 (p2.t2 = 900+450 = 1,350) answering in the negative;


(1+2) BIFURCATES (insufficient, therefore answer is E):

Same examples as in (2) , because there (in both cases) I used t1 > t2 as sttm (1) asks/restricts!!

Regards,
Fabio.
Fabio Skilnik :: GMATH method creator ( Math for the GMAT)
English-speakers :: https://www.gmath.net
Portuguese-speakers :: https://www.gmath.com.br
Top
Post new topic Post Reply
• Page 1 of 1