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605-655 Level|   Geometry|            
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Bunuel
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Bunuel
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second statement is not sufficient. B'se QT may be equal to RT, but need not be equal to QR. so 2 is insufficient
So i believe answer will be 'A' :roll:
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1. PS=QR=4
Since , QTR is equilateral
QT=TR=QR=4
Triangles QTP and RTS are congruent(RHS)
=>PT=TS
Now using pythagorean theorem , we can find out QP or RS .
QT^2= QP^2 + PT^2
And calculate the area of rectangle PQRS.
Sufficient

2. PT=TS = 2
Triangles QTP and RTS are congruent (SAS)
=> QT=RT
But we have no can conclude whether QT/RT is equal to QR .
Hence, insufficient.

Answer A
:|
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Hmm... was too fast about B, missed the point... B is not sufficient
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Bunuel

In rectangular region PQRS above, T is a point on side PS. If PS = 4, what is the area of region PQRS?

(1) Triangle QTR is equilateral.
(2) Segments PT and TS have equal length.

Kudos for a correct solution.

Attachment:
2015-10-08_1851.png

SOLUTION:

Statement 1: If Triangle QTR is equilateral. then QR=QT=4, And also every angle of this Triangle is 60 degrees.
then Triangle QTP is 30-60-90 right triangle then the sides of triangle PQT are in ratio 1:\(\sqrt{3}\):2.

if longest side QT=4, then PQ must be 2*\(\sqrt{3}\).

we now know lengths of adjacent sides , we can calculate area of rectangle.

So , Statement 1 is SUFFICIENT.

Statement 2: we know PT, but we don't know anything about type of a triangle or lengths of PQ or QT.

So, Statement 2 is INSUFFICIENT.

ANS: A.

Hope i am not missing anything about Statement 2.
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The correct answer must be D
If PT = PS , then we already know QP=RS , Hence QT = RT . Therefore triangles QPT and RTS are congruent (RHS) .
Angles TQR and QRT are equal ( As QT=RT) .
Angles QTP and RTS are equal ( Congruent triangles) .
Angle QTR = 180 - 2(angle TQR) = 180 - 2(angle QTP)
Therefore angle TQR = QTP , which implies TQR=QTP=RTS
Therefore an equilateral triangle , Hence we can find the area .
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4d

In rectangular region PQRS above, T is a point on side PS. If PS = 4, what is the area of region PQRS?

(1) Triangle QTR is equilateral.
(2) Segments PT and TS have equal length.

The correct answer must be D
If PT = PS , then we already know QP=RS , Hence QT = RT . Therefore triangles QPT and RTS are congruent (RHS) .
Angles TQR and QRT are equal ( As QT=RT) .
Angles QTP and RTS are equal ( Congruent triangles) .
Angle QTR = 180 - 2(angle TQR) = 180 - 2(angle QTP)
Therefore angle TQR = QTP , which implies TQR=QTP=RTS
Therefore an equilateral triangle , Hence we can find the area .

The correct answer is given under the spoiler in the original post and it's A. For (2) all we k now is one side of the rectangle. Having T as the midpoint of PS gives us nothing.

Hope it helps.
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Yes i have seen the answer .
But i proved that if T is the midpoint then the resulting triangle will be equilateral .
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Yes i have seen the answer .
But i proved that if T is the midpoint then the resulting triangle will be equilateral .


Hi,
check the angles which are equal..
the Triangle is QRT
and your solution says

Quote:
Therefore angle TQR = QTP , which implies TQR=QTP=RTS
Therefore an equilateral triangle , Hence we can find the area .
The angle which has to be shown EQUAL are QRT = RTQ = TQR..
Statement 2 is not sufficient..
relook in your solution

Logically, I will give you ONE rectangle..
1) It has 100 as length and ONLY 1 as width..
try it out, it can never have all angles as 60 degree as the two equal sides will be CLOSE to 50-60 and the third side will be 100..
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Statement 1) “QTR is an equilateral triangle” If this is true then with QR as the base and the height equivalent to the side PQ (or RS). Then the measure of the of the triangle is ½ of the measure of the rectangle since the triangle QTR would essentially be LW/ 2. You can determine the area of triangle QTR using the formula for the area of an equilateral triangle
“\((s^2\sqrt{3})/4\).”

(the facts tell you that “s = 4”) This is sufficient. The answer is A or D.

I got this right but I'm curios how it would help us if we find the area of QTR to find the area of the rectangle.
can some one address the query?
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Bunuel

In rectangular region PQRS above, T is a point on side PS. If PS = 4, what is the area of region PQRS?

(1) Triangle QTR is equilateral.
(2) Segments PT and TS have equal length.

Kudos for a correct solution.

Attachment:
2015-10-08_1851.png

For an equilateral triangle, all the angles are equal to 60 degree.
So ag(QRT)+ag(TRS)=90
ag(TRS)= 30degree

which means: ag(RTS) = 60 and ag(RST)=90

Sin 60 = root3/2

RS/RT=root3/2

RS=2root3


area= RS*PS

1 suff
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(1) PQ=PS=4
Since QTR is equilateral then, knowing the value of one side we can easility calculate the altitude,using the followign formula:
h=a*3^1/2/2=4*3^1/2/2=2*3^1/2 Sufficient
(2) Defferent values are possible and since we are lacking any information about angles it's completely insufficient.
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OFFICIAL EXPLANATION:

It is given that PQRS is a rectangle and PS = 4. The area of PQRS can be determined if and only if PQ can be determined.

1) It is given that ΔQTR is equilateral. If 62823.png is the height of ΔQTR as shown above, then ΔQUT is a 30−60−90° triangle with UR = 2. Using the ratios for 30−60−90 triangles, TU = 62832.png. Since PQ = TU, the area of PQRS can be determined; SUFFICIENT.

2) Given that PT = TS, PQ could be any positive number. Thus, it is not possible to determine PQ and therefore not possible to determine the area of PQRS; NOT sufficient.

The correct answer is A;
statement 1 alone is sufficient.

Attachments

a1.JPG
a1.JPG [ 11.65 KiB | Viewed 25397 times ]

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Bunuel

In rectangular region PQRS above, T is a point on side PS. If PS = 4, what is the area of region PQRS?

(1) Triangle QTR is equilateral.
(2) Segments PT and TS have equal length.


DS77302.01

Project DS Butler: Day 36: Data Sufficiency (DS72)


For DS butler Questions Click Here

Attachment:
2015-10-08_1851.png

ANswer: Option A

GMATinsight's Solution



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