Find all School-related info fast with the new School-Specific MBA Forum

It is currently 22 May 2015, 19:12

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.

Events & Promotions

Events & Promotions in June
Open Detailed Calendar

In triangle ABC, angle ABC is 90 degrees. What the perimeter

  Question banks Downloads My Bookmarks Reviews Important topics  
Author Message
TAGS:
CEO
CEO
User avatar
Joined: 21 Jan 2007
Posts: 2764
Location: New York City
Followers: 9

Kudos [?]: 354 [0], given: 4

In triangle ABC, angle ABC is 90 degrees. What the perimeter [#permalink] New post 26 Dec 2007, 10:49
In triangle ABC, angle ABC is 90 degrees.
What the perimeter of triangle ABC?

1. AB + BC = 7
2. AB/BC = 3/4

Can someone tell me why statement 1 is insuff. if we shift the values between AB and BC, the total of these two sides will still be 7. how does it affect the perimeter?
1 KUDOS received
Director
Director
User avatar
Joined: 08 Jun 2007
Posts: 584
Followers: 2

Kudos [?]: 80 [1] , given: 0

Re: perimeter of a triangle [#permalink] New post 26 Dec 2007, 11:26
1
This post received
KUDOS
bmwhype2 wrote:
In triangle ABC, angle ABC is 90 degrees.
What the perimeter of triangle ABC?

1. AB + BC = 7
2. AB/BC = 3/4

Can someone tell me why statement 1 is insuff. if we shift the values between AB and BC, the total of these two sides will still be 7. how does it affect the perimeter?


if you shift values , total will remain same but the hypotenuse will change which affects the perimeter.

C.
Expert Post
CEO
CEO
User avatar
Joined: 17 Nov 2007
Posts: 3577
Concentration: Entrepreneurship, Other
Schools: Chicago (Booth) - Class of 2011
GMAT 1: 750 Q50 V40
Followers: 408

Kudos [?]: 2168 [0], given: 359

GMAT ToolKit User Premium Member
 [#permalink] New post 26 Dec 2007, 10:56
Expert's post
1)

P= AB + BC + AC = (AB + BC) + √(AB² + BC²) = 7 + √(AB² + (7-AB)²) =
=7+√(AB² + (7-AB)²) = 7+√(2AB² - 14AB +49)

2AB² - 14AB +49 is not constant.
Director
Director
User avatar
Joined: 12 Jul 2007
Posts: 865
Followers: 13

Kudos [?]: 221 [0], given: 0

 [#permalink] New post 26 Dec 2007, 10:58
A^2+B^2=C^2 for the sides of a right triangle with the legs being A and B and the hypotenuse being C.

1. tells us the two legs add up to 7.

3^3+4^2=25 so the legs are 3-4-5 for a perimeter of 12

BUT they could also be 5 and 2 since 5+2 = 7 (or they could be 6 and 1)

2^2+5^2=29 so the legs would be 2-5-sqrt(29) for a different perimeter altogether.

2. AB/BC tells us the ratio of the two legs is 3/4. This is insufficient on it's own as the legs could be 3-4, 9-12, 30-40...any two numbers in the 3/4 ratio.

HOWEVER, when taken together...we know the ratio between the two legs is 3/4 and they must add up to 7. This means the only possible values for the legs are 3 and 4. Giving the entire perimeter 3+4+5 or 12

Answer is C
Manager
Manager
User avatar
Affiliations: The Earth organization, India
Joined: 25 Dec 2010
Posts: 193
WE 1: SAP consultant-IT 2 years
WE 2: Entrepreneur-family business 2 years
Followers: 5

Kudos [?]: 11 [0], given: 12

Re: perimeter of a triangle [#permalink] New post 15 Jun 2011, 00:04
this question might seem lame, but I am missing a concept,

ab+bc = 7 and abc = 90 degree, does this not imply we have a 3-4-5 triangle here ?

are other values of ab and bc are possible with abc = 90 degree ?
_________________

Cheers !!

Quant 47-Striving for 50
Verbal 34-Striving for 40

Math Forum Moderator
avatar
Joined: 20 Dec 2010
Posts: 2031
Followers: 137

Kudos [?]: 1128 [0], given: 376

Re: perimeter of a triangle [#permalink] New post 20 Jun 2011, 01:34
bblast wrote:
this question might seem lame, but I am missing a concept,

ab+bc = 7 and abc = 90 degree, does this not imply we have a 3-4-5 triangle here ?

are other values of ab and bc are possible with abc = 90 degree ?


does this not imply we have a 3-4-5 triangle here ?
No, it doesn't imply so. That is just one of the infinite possibilities.

ab=1, bc=6, ac= \(\sqrt{1^2+6^2}=\sqrt{37}\)
ab=2.11, bc=4.89, ac= \(\sqrt{(2.11)^2+(4.89)^2}\)
_________________

~fluke

GMAT Club Premium Membership - big benefits and savings

Expert Post
Veritas Prep GMAT Instructor
User avatar
Joined: 16 Oct 2010
Posts: 5536
Location: Pune, India
Followers: 1366

Kudos [?]: 6951 [0], given: 178

Re: perimeter of a triangle [#permalink] New post 21 Jun 2011, 02:25
Expert's post
Let me point out here that Pythagorean triplets (3,4,5 etc) give you the sides of a right angled triangle such that each side is an integer. But the sides of a right angled triangle needn't necessarily be integers.
If it is given that hypotenuse is 5, the sides could be 3,4 or they could be 1, \(\sqrt{24}\) or 2, \(\sqrt{21}\) etc...
Similarly, if sum of the legs is 7, the sides could be 3,4 or 1,6 or 2,5 etc... For each of these, the hypotenuse will be different.

What helps in visualizing whether there are multiple solutions is drawing. Make a hypotenuse of length 5 cm. As you keep changing the incline of the hypotenuse, you keep getting different values for the other two sides.
_________________

Karishma
Veritas Prep | GMAT Instructor
My Blog

Get started with Veritas Prep GMAT On Demand for $199

Veritas Prep Reviews

Re: perimeter of a triangle   [#permalink] 21 Jun 2011, 02:25
    Similar topics Author Replies Last post
Similar
Topics:
5 Experts publish their posts in the topic For triangle ABC, angle ABC = 90 degrees, and side AC has a length of Bunuel 5 02 Feb 2015, 06:20
1 In triangle ABC angle ABC is 90 degrees. What is the vishalgc 13 11 Oct 2008, 06:02
In triangle ABC angle ABC is 90 degrees. What is the sondenso 9 11 May 2008, 23:27
2 Are all the angles of triangle ABC smaller than 90 degrees? bmwhype2 14 20 Dec 2007, 13:14
Are all the angles of Triangle ABC smaller than 90 degrees? bz9 7 21 Feb 2007, 03:43
Display posts from previous: Sort by

In triangle ABC, angle ABC is 90 degrees. What the perimeter

  Question banks Downloads My Bookmarks Reviews Important topics  


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

Powered by phpBB © phpBB Group and phpBB SEO

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®.