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Figure ABCD is a rectangle with sides of length x centimete [#permalink]
15 Jul 2007, 18:45

00:00

A

B

C

D

E

Difficulty:

25% (medium)

Question Stats:

73% (02:02) correct
27% (01:18) wrong based on 101 sessions

Attachment:

Untitled.png [ 7.04 KiB | Viewed 815 times ]

Figure ABCD is a rectangle with sides of length x centimeters and width y centimeters, and a diagonal of length z centimeters. What is the measure, in centimeters, of the perimeter of ABCD ?

Re: Figure ABCD is a rectangle with sides of length x [#permalink]
03 Feb 2014, 03:12

dynocomet wrote:

Figure ABCD is a rectangle with sides of length x centimeters and width y centimeters, and a diagonal of length z centimeters. What is the measure, in centimeters, of the perimeter of ABCD? (The diagram shows line segment AD labeled as "x" and line segment DC labeled as "y")

(1) x - y = 7 (2) z = 13

I read that the answer is C, but cannot understand why. First of all, statement 1 seems like a contradiction -- how can the hypotenuse be SMALLER than either of the two sides?

Thanks.

The answer to the questions shows C. However why can we not state that from statement (2) we are dealing with a 5,12,13 triangle? Hence B would be sufficient to answer the question.

Re: Figure ABCD is a rectangle with sides of length x [#permalink]
03 Feb 2014, 04:37

Expert's post

Mattd wrote:

dynocomet wrote:

Figure ABCD is a rectangle with sides of length x centimeters and width y centimeters, and a diagonal of length z centimeters. What is the measure, in centimeters, of the perimeter of ABCD? (The diagram shows line segment AD labeled as "x" and line segment DC labeled as "y")

(1) x - y = 7 (2) z = 13

I read that the answer is C, but cannot understand why. First of all, statement 1 seems like a contradiction -- how can the hypotenuse be SMALLER than either of the two sides?

Thanks.

The answer to the questions shows C. However why can we not state that from statement (2) we are dealing with a 5,12,13 triangle? Hence B would be sufficient to answer the question.

The point is that a right triangle with hypotenuse 13, doesn't mean that we have (5, 12, 13) right triangle. If we are told that the lengths of all sides are integers, then yes: the only integer solution for right triangle with hypotenuse 13 would be (5, 12, 13). Or in other words: x^2+y^2=13^2 DOES NOT mean that x=5 and y=12. Certainly this is one of the possibilities but definitely not the only one. In fact x^2+y^2=13^2 has infinitely many solutions for x and y and only one of them is x=5 and y=12.

For example: x=1 and y=\sqrt{168} or x=2 and y=\sqrt{165}...

So knowing that the diagonal of a rectangle (hypotenuse) equals to one of the Pythagorean triple hypotenuse values is not sufficient to calculate the sides of this rectangle.

Re: Figure ABCD is a rectangle with sides of length x centimete [#permalink]
15 Jul 2014, 01:13

How can we use the both statement to find the answer? I marked B and Bunuel explained how it is wrong. My second answer would be E I mean I know 12-5 = 7 and that with z =13 so we can say that three sides "can" be 5,12,13 but can we say that's the only possible value?

Figure ABCD is a rectangle with sides of length x centimete [#permalink]
15 Jul 2014, 01:35

Expert's post

b2bt wrote:

How can we use the both statement to find the answer? I marked B and Bunuel explained how it is wrong. My second answer would be E I mean I know 12-5 = 7 and that with z =13 so we can say that three sides "can" be 5,12,13 but can we say that's the only possible value?

Given that x - y = 7 and z = 13. We also know that x^2 + y^2 = z^2 = 169. We want to find the perimeter which is 2x+2y = 2(x+y).