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Re: One more geometry [#permalink]
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Hussain15 wrote:
What is the perimeter of rectangle R?

(1) The area of rectangle R is 60.

(2) The length of a diagonal of rectangle R is 13.

I wanna discuss this one in detail.


Let the sides be \(x\) and \(y\). Question: \(P=2(x+y)=?\)

(1) \(area=xy=60\). Clearly insufficient.
(2) \(x^2+y^2=13^2=169\). Also insufficient.

(1)+(2) Square P --> \(P^2=4(x+y)^2=4(x^2+2xy+y^2)\) as from (1) \(xy=60\) and from (2) \(x^2+y^2=169\), then \(P^2=4(x^2+2xy+y^2)=4(169+120)=4*289\) --> \(P=\sqrt{4*289}=2*17=34\). Sufficient.

Answer: C.
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Re: One more geometry [#permalink]
OA is "C", but why??? It should be "B". We know the 13-12-5 principle. If hypotenuse is 13, then the other two sides can be determined.
Why not "B"?????

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Re: One more geometry [#permalink]
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Hussain15 wrote:
OA is "C", but why??? It should be "B". We know the 13-12-5 principle. If hypotenuse is 13, then the other two sides can be determined.
Why not "B"?????


What about \(13-\frac{13}{\sqrt{2}}-\frac{13}{\sqrt{2}}\) ?
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Re: One more geometry [#permalink]
No this is wrong. a^2+b^2 = 13^2 holds true for many values of (a,b)

You cannot deduce a and b to be 12,5

what if a^2 = 6 and b^=7, it was not even given that they have integral value. Even if it was given a and b are integers you still have to think whether any integral pair a,b exists which is unique.

no doubt 2+2 = 4, but you can not deduce 4 = 2+2 only...it can be 3+1....This reasoning will help you in CR - cause and effect.
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Re: One more geometry [#permalink]
Hussain15 wrote:
OA is "C", but why??? It should be "B". We know the 13-12-5 principle. If hypotenuse is 13, then the other two sides can be determined.
Why not "B"?????

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ans c
I am no Math Genius ..but if you deduce this a^2 +b^2=C^2..then it doesn't mean that triplet a,b, c are pythgorean triplet.

But if a right angle triangle is given ..then yes a,b,c satisfy pythagoras theorem and if c is given then you can find a and b.
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Re: One more geometry [#permalink]
Kudos for the help. Now I got this point. :)
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Re: One more geometry [#permalink]
Hussain15 wrote:
OA is "C", but why??? It should be "B". We know the 13-12-5 principle. If hypotenuse is 13, then the other two sides can be determined.
Why not "B"?????

Posted from my mobile device


Dude,

Not Every Red car is Ferrari ... :)

Just kidding... 8-)

So every triplet is not 13-12-5
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Re: One more geometry [#permalink]
When can you use the x:x:x√2 ratio for triangles, i thought you could on a 90 45 45 triangle?
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Re: What is the perimeter of rectangle R? [#permalink]
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Re: What is the perimeter of rectangle R? [#permalink]
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