GMAT Software Geometry Question

Expert replies

mpaudena: Senior | Next Rank: 100 Posts; Posts: 80; Joined: Wed Jun 04, 2008 1:16 pm; Thanked: 3 times

by mpaudena » Tue Mar 03, 2009 4:17 pm

Hello GMAT Beaters. First, thanks in advance for the response. Second, on the GMAT software I came upon a geometry question that goes as follows:

The perimeter of a certain isosceles triangle is 16 + 16(square root of 2). What is the length of the hypotenuse of the triangle?

I can't seem to figure out how they came up with the answer. Please help. Thanks.

Like this post

Source: Beat The GMAT — Problem Solving | Tue Mar 03, 2009 4:17 pm

crossingfingers: Junior | Next Rank: 30 Posts; Posts: 23; Joined: Wed Apr 18, 2007 7:09 am; Thanked: 1 times

by crossingfingers » Tue Mar 03, 2009 5:29 pm

The perimeter of a right angled isosceles triangle is: 2a + b where 2a are the 2 equal sides and b is the unequal side...

we have 16 + 16 (sq root 2).

Now I used the POE:

if 2a=16 a=8...then b = 16(sq root 2) doesnt make sense

if 2a= 16(sq root 2) a=8(sq root 2)...then b=hyp=16 makes sense.
you can get it from the 1:1:sq root 2 property of an isosceles right triangle or u can use Pythagoras theorem to solve to check.

Not sure if this is the standard approach.

Like this post

mpaudena: Senior | Next Rank: 100 Posts; Posts: 80; Joined: Wed Jun 04, 2008 1:16 pm; Thanked: 3 times

by mpaudena » Tue Mar 03, 2009 5:37 pm

crossingfingers wrote:The perimeter of a right angled isosceles triangle is: 2a + b where 2a are the 2 equal sides and b is the unequal side...

we have 16 + 16 (sq root 2).

Now I used the POE:

if 2a=16 a=8...then b = 16(sq root 2) doesnt make sense

if 2a= 16(sq root 2) a=8(sq root 2)...then b=hyp=16 makes sense.
you can get it from the 1:1:sq root 2 property of an isosceles right triangle or u can use Pythagoras theorem to solve to check.

Not sure if this is the standard approach.

Thanks crossing fingers but first what is POE? Second, why did you think that the first choice didn't make sense? Is it cause you tried the properties of isoscelese and it didn't work?

Like this post

mpaudena: Senior | Next Rank: 100 Posts; Posts: 80; Joined: Wed Jun 04, 2008 1:16 pm; Thanked: 3 times

by mpaudena » Tue Mar 03, 2009 5:41 pm

Also does anyone know how to do this algebraically cause I'm sure this will not be the exact question on the test and I want to understand the concept that I'm missing. Thanks.

Like this post

crossingfingers: Junior | Next Rank: 30 Posts; Posts: 23; Joined: Wed Apr 18, 2007 7:09 am; Thanked: 1 times

by crossingfingers » Tue Mar 03, 2009 5:42 pm

oops...sorry...POE - process of elimination (am pretty much doing an either or)

yes...for the first choice applying Pythagoras theorem a^2 + a^2 = b^2...gives us sq root of (64 + 64) = 8(sq root of 2) which is not what's expected - 16(sq root of 2). Hence proceed to 2

Like this post

mridula: Senior | Next Rank: 100 Posts; Posts: 44; Joined: Tue Feb 03, 2009 5:17 am

by mridula » Tue Mar 03, 2009 8:57 pm

what is the OA?

Like this post

mpaudena: Senior | Next Rank: 100 Posts; Posts: 80; Joined: Wed Jun 04, 2008 1:16 pm; Thanked: 3 times

by mpaudena » Wed Mar 04, 2009 2:26 am

Does anyone know how to do this algebraically cause I'm sure this will not be the exact question on the test and I want to understand the concept that I'm missing. Thanks.

Like this post

farooq: Master | Next Rank: 500 Posts; Posts: 140; Joined: Sat Feb 28, 2009 8:51 amFollowed by: 3 members; Location: India; Thanked: 14 times

by farooq » Wed Mar 04, 2009 6:55 am

crossingfingers wrote:The perimeter of a right angled isosceles triangle is: 2a + b where 2a are the 2 equal sides and b is the unequal side...

we have 16 + 16 (sq root 2).

Now I used the POE:

if 2a=16 a=8...then b = 16(sq root 2) doesnt make sense

if 2a= 16(sq root 2) a=8(sq root 2)...then b=hyp=16 makes sense.
you can get it from the 1:1:sq root 2 property of an isosceles right triangle or u can use Pythagoras theorem to solve to check.

Not sure if this is the standard approach.

But where it is mentioned that the triangle is right angle triangle

Regards,
Farooq Farooqui.
London. UK

It is your Attitude, not your Aptitude, that determines your Altitude.

Like this post

mpaudena: Senior | Next Rank: 100 Posts; Posts: 80; Joined: Wed Jun 04, 2008 1:16 pm; Thanked: 3 times

by mpaudena » Wed Mar 04, 2009 7:41 am

farooq wrote:
crossingfingers wrote:The perimeter of a right angled isosceles triangle is: 2a + b where 2a are the 2 equal sides and b is the unequal side...

we have 16 + 16 (sq root 2).

Now I used the POE:

if 2a=16 a=8...then b = 16(sq root 2) doesnt make sense

if 2a= 16(sq root 2) a=8(sq root 2)...then b=hyp=16 makes sense.
you can get it from the 1:1:sq root 2 property of an isosceles right triangle or u can use Pythagoras theorem to solve to check.

Not sure if this is the standard approach.
But where it is mentioned that the triangle is right angle triangle

Sorry about that guys. I neglected to write that it was a right triangle. Crossingfingers was correct both in the answer and in that it was a right triangle.

Last edited by mpaudena on Wed Mar 04, 2009 3:08 pm, edited 1 time in total.

Like this post

mkbigmoz: Senior | Next Rank: 100 Posts; Posts: 49; Joined: Sun Feb 08, 2009 4:53 pmFollowed by: 1 member; Thanked: 3 times

by mkbigmoz » Wed Mar 04, 2009 2:59 pm

What was the answer? You can put it in a spoiler

Like this post

Post new topic Post Reply

• Page 1 of 1

GMAT Course Reviews

560 reviews

1168 reviews

431 reviews

359 reviews

147 reviews

5/5

5 Star (560 Reviews)

"Target Test Prep is the closest to the official version of the GMAT exam, about 99% accuracy in terms of the quality and quantity of information. The course has excellently created singular sets of focused lessons and tests for every possible topic that one could come across in the official GMAT exam."

"The TTP course maximizes the efficiency of the time you spend studying. It will take time and effort but I could almost guarantee that if you complete the course exactly as it is laid out you will get an amazing score. They also have a very responsive team willing to help with any questions you might have."

"TTP has two things that I think no other test prep company offers: A teaching approach that reinforces understanding and an attitude that will give you the mental preparedness needed to succeed on the test. TTP gives you a deep understanding of the concept you need to know while teaching you how to think."

Write a Review