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## GMAT prep decimal

This topic has 11 member replies
arorag GMAT Destroyer!
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GMAT prep decimal Sun May 04, 2008 5:01 pm
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• Lap #[LAPCOUNT] ([LAPTIME])
What is the hundredth digit of the decimal Z?
1. The tenth digit of 100Z is 2
2. The unit digit of 1000Z is 2

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amitansu Really wants to Beat The GMAT!
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Sun May 04, 2008 10:16 pm
E is the answer.

jain0069 Just gettin' started!
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Mon May 05, 2008 1:53 am
I think the answer is D.

Here's how..

1. The tenth digit of 100Z is 2.

Therefore:

100Z = .2XXXXXX (the X's dont matter)
Hence,
Z = .2XXXX / 100
Or
Z = .002XXXXX

So the hundredth digit of Z is 0. Sufficient.

2. The unit digit of 1000Z is 2. This is basically saying the same thing as statement 1. However, just taking this alone:

1000Z = 2.XXXXX (again the X's dont matter)
Hence,
Z = 2.XXXXX / 1000
Or
Z = .002XXXX

So the hundredth digit of Z is 0. Sufficient Again.

Therefore the answer is D.

simplyjat GMAT Destroyer!
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Mon May 05, 2008 1:59 am
jain0069 wrote:
I think the answer is D.

Here's how..

1. The tenth digit of 100Z is 2.

Therefore:

100Z = .2XXXXXX (the X's dont matter)
Hence,
Z = .2XXXX / 100
Or
Z = .002XXXXX

So the hundredth digit of Z is 0. Sufficient.

2. The unit digit of 1000Z is 2. This is basically saying the same thing as statement 1. However, just taking this alone:

1000Z = 2.XXXXX (again the X's dont matter)
Hence,
Z = 2.XXXXX / 1000
Or
Z = .002XXXX

So the hundredth digit of Z is 0. Sufficient Again.

Therefore the answer is D.
You are wrong in assuming
100Z = .2XXXXXX
actually it should be
100Z = XXXX.2XXXXXX

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jain0069 Just gettin' started!
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Mon May 05, 2008 2:02 am
Jeez... *** Slap across the face ***... Thanks dude... Just tells me why I am so bad at DS eh ...

Note to self: Will always triple and quadruple check my answers before posting again...

Thanks for pointing out the mistake in my reasoning though...

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simplyjat GMAT Destroyer!
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Mon May 05, 2008 2:16 am
jain0069 wrote:
Jeez... *** Slap across the face ***... Thanks dude... Just tells me why I am so bad at DS eh ...

Note to self: Will always triple and quadruple check my answers before posting again...

Thanks for pointing out the mistake in my reasoning though...
Don't be harsh on yourself, DS just requires some practice and patience.

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simplyjat

antyagi Just gettin' started!
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Mon May 05, 2008 3:15 am
I could not get the solution of the problem.

Can someone please explain the final answer of the problem please ?

Is it E ?

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doclkk Really wants to Beat The GMAT!
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Tue Jul 07, 2009 10:40 pm
arorag wrote:
What is the hundredth digit of the decimal Z?
1. The tenth digit of 100Z is 2
2. The unit digit of 1000Z is 2
E for sure

1. Doesn't tell you hundreths
2. Doesn't tell you hundreths

What else is there to consider?

abhinav85 Really wants to Beat The GMAT!
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Wed Jul 08, 2009 10:57 am
IMO B

What is the OA arorag?

karthikpandian19 GMAT Titan
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Mon May 14, 2012 1:01 am
OA is E,

Can any GMAT EXPERT provide detailed explanation for this as my answer is tending towards A

eagleeye GMAT Destroyer!
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Mon May 14, 2012 1:32 am
All right, I am going to settle this debate. btw, the correct answer is E. Here's how.

"What is the hundredth digit of the decimal Z?
1. The tenth digit of 100Z is 2
2. The unit digit of 1000Z is 2"

Let Z =abcd.efgh (where a,b,c,d,e,f,g,h are all integers) (we can go farther on each side, lets just assume this without loss of much generality). The hundredth digit here is f; if we can determine d either from 1 or 2 or both, the answer won't be E.

Now:
1. 100Z = abcdef.gh; The tenth digit is 2. So, g = 2.
therefore, 100Z=abcdef.2h
No, information about f, INSUFFICIENT.

2. 1000Z = abcdefg.h ; The unit digit is g again, so g = 2.
therefore, 1000Z = abcdef2.h
Again, we don't know what f is, INSUFFICIENT.

Now let's consider them together. Both equations give the same information, i.e. g = 2. Hence C is not a possibility as well. Therefore the correct answer is E.

Point to note: if we were not given the same information (g = 2) in the two equations, we might have been able to find f by subtracting the two equations, or substituting.

Let me know if this helps

GmatKiss GMAT Titan
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Mon May 14, 2012 4:32 am
IMO: E

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