jigz wrote:

Hi! I'm a lurker, who has decided to start posting because I need desperate help!

I took the Official GMAT Practice test and got some DS and PS questions wrong, but I can't figure out why. Can someone please help? Below are the questions and the answers I thought were accurate (OE also specified)

1) The perimeter of an isosceles triangle is 16 + 16\sqrt{2} What is the length of the hypotenuse?

a) 8

b) 16

c) 4\sqrt{2}

d) 8\sqrt{2}

e) 16\sqrt{2}

OE is B but I can't understand how?

We are assuming that it is a right angled traingle as it is asking for hypotenuse..but as far as i know, we know not assume anything in GMAT..anyways..

If perimeter is 16 + 16 sqr2 then answer is 16,

Since, triangle is isosceles,it's perimeter = x+x + (sqr2)x = 2x+xsqr2 = 16 + 16 sqr2

=x =16/sqr2

hence, hypotenuse = (16/sqr2) * sqr2 = 16...