nasahtahir wrote:
I understand but again correct me if I'm wrong isn't our target question "What is the perimeter" ?
Sure with the process we found out x=y that means it is an isosceles triage so what? We would still require the 1 more side if not two. Please explain :s

Hi nasahtahir,

An isosceles right triangle is a 45/45/90 triangle, so knowing that - if we have one of the sides, then we can figure out the other two sides. In this case, knowing that the hypotenuse is 10 would allow us to figure out the other two sides (and the total perimeter) - so we don't actually have to do the 'math work.'

GMAT assassins aren't born, they're made,
Rich

Hi nasahtahir,

If the only information that you have is the information in the prompt, then you can't answer the given question (in DS prompts, the information provided is NEVER enough to answer the question that is asked). Your 'job' is to determine whether either of the included Facts underneath the prompt is enough additional data to answer the question.

From the prompt, you are correct that X^2 + Y^2 = 100. With the information in Fact 2 though, you know that the two legs are equation, so the equation becomes...

X^2 + X^2 = 100

Mitch has actually already done all of the math already (in his solution), if you'd like to see it.

GMAT assassins aren't born, they're made,
Rich