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# GMAT Practice Test answer explanations

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Intern
Joined: 10 Jun 2009
Posts: 7

Kudos [?]: 7 [0], given: 0

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30 Aug 2009, 05:49
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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?

2) Value of 10^8 - 10^2/10^7-10^3 is closest to which of the following:

a) 1
b) 10
c) 10^2
d) 10^3
e) 10^4

I simplified it to read 10^6/10^4 = C, but OE is B and I don't know where I'm messing up.

3) When a tree was first planted, it was 4ft tall, and the height of the tree increased by a constant amount each year for six years. At the end of the sixth year, the tree was 1/5th taller than it was at the end of the 4th year. By how many ft. did the tree increase each year?

a) 3/10
b) 2/5
c) 1/2
d) 2/3
e) 6/5

I just guessed 2/3, but I cant form an accurate equation to solve it. I selected x as the constant, so the most I could get was: 4 + 5x = 4 + 3x + 1/5 (4+3x)

I am also unconvinced about some of the answers to the DS questions, which I will post in the appropriate forum.

Kudos [?]: 7 [0], given: 0

Manager
Joined: 14 Aug 2009
Posts: 121

Kudos [?]: 113 [0], given: 13

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30 Aug 2009, 06:23
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?

2) Value of 10^8 - 10^2/10^7-10^3 is closest to which of the following:

a) 1
b) 10
c) 10^2
d) 10^3
e) 10^4

I simplified it to read 10^6/10^4 = C, but OE is B and I don't know where I'm messing up.

3) When a tree was first planted, it was 4ft tall, and the height of the tree increased by a constant amount each year for six years. At the end of the sixth year, the tree was 1/5th taller than it was at the end of the 4th year. By how many ft. did the tree increase each year?

a) 3/10
b) 2/5
c) 1/2
d) 2/3
e) 6/5

I just guessed 2/3, but I cant form an accurate equation to solve it. I selected x as the constant, so the most I could get was: 4 + 5x = 4 + 3x + 1/5 (4+3x)

I am also unconvinced about some of the answers to the DS questions, which I will post in the appropriate forum.

Q1 is wrong?

Q2 is also wrong? if it is (10^8-10^2)/(10^7-10^3) = 10^8/10^7=10

Q3 is quite clear
4+6x=(6/5)*(4+4x)
x=2/3
_________________

Kudos me if my reply helps!

Kudos [?]: 113 [0], given: 13

Manager
Joined: 25 Aug 2009
Posts: 174

Kudos [?]: 110 [0], given: 12

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30 Aug 2009, 06:38
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...

Kudos [?]: 110 [0], given: 12

Intern
Joined: 10 Jun 2009
Posts: 7

Kudos [?]: 7 [0], given: 0

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30 Aug 2009, 06:52
Thanks a lot! I'm a bit embarassed - I got most of the difficult problems right, but managed to screw up the most basic ones!

Kudos [?]: 7 [0], given: 0

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