Extremely embarassing, can't do long division on recurring d : GMAT Quantitative Section
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# Extremely embarassing, can't do long division on recurring d

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Manager
Joined: 10 Sep 2012
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Extremely embarassing, can't do long division on recurring d [#permalink]

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04 Nov 2012, 16:30
Curly brackets {} around the last digits of a decimal fraction signify that these digits recur an infinite number of times. For example 0.1{5} is a shorthand for 0.1555555… Similarly, 0.{15} is a shorthand for 0.15151515….
10/99 is which of the following?

0.{11}
0.{101}
0.{10}
0.{09}
0.{01}

So the answer to this is obvious (to anyone that can do long division), unfortunately I haven't done this type of LD since HS and I need a refresher.

The answer is C but I'm failing to understand why there is only 1 zero between the 1s. In the long division process we subtract 99 from 100, leaving 1. Therefore we have to add 2 zeroes to get back to 100 where we can multiply 99 into 1 again to get 100-99... but this obviously is not the case and I'm struggling to understand why.

Can anyone help me out? I've attached a picture of my work...

Thank you so much guys

Director
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Re: Extremely embarassing, can't do long division on recurring d [#permalink]

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04 Nov 2012, 21:20
1
KUDOS
anon1 wrote:
Curly brackets {} around the last digits of a decimal fraction signify that these digits recur an infinite number of times. For example 0.1{5} is a shorthand for 0.1555555… Similarly, 0.{15} is a shorthand for 0.15151515….
10/99 is which of the following?
0.{11}
0.{101}
0.{10}
0.{09}
0.{01}
So the answer to this is obvious (to anyone that can do long division), unfortunately I haven't done this type of LD since HS and I need a refresher.
The answer is C but I'm failing to understand why there is only 1 zero between the 1s. In the long division process we subtract 99 from 100, leaving 1. Therefore we have to add 2 zeroes to get back to 100 where we can multiply 99 into 1 again to get 100-99... but this obviously is not the case and I'm struggling to understand why.
Can anyone help me out? I've attached a picture of my work...
Thank you so much guys

Try dividing this first: 100000/99
And then come back and try dividing 10.0000/99
Compare these 2 calculations (specially the second one to your calculation)

Hopefully you'll see the underlying concept and results
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Re: Extremely embarassing, can't do long division on recurring d [#permalink]

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05 Nov 2012, 23:30
1
KUDOS
Expert's post
anon1 wrote:
Curly brackets {} around the last digits of a decimal fraction signify that these digits recur an infinite number of times. For example 0.1{5} is a shorthand for 0.1555555… Similarly, 0.{15} is a shorthand for 0.15151515….
10/99 is which of the following?

0.{11}
0.{101}
0.{10}
0.{09}
0.{01}

So the answer to this is obvious (to anyone that can do long division), unfortunately I haven't done this type of LD since HS and I need a refresher.

The answer is C but I'm failing to understand why there is only 1 zero between the 1s. In the long division process we subtract 99 from 100, leaving 1. Therefore we have to add 2 zeroes to get back to 100 where we can multiply 99 into 1 again to get 100-99... but this obviously is not the case and I'm struggling to understand why.

Can anyone help me out? I've attached a picture of my work...

Thank you so much guys

You may want to check out khanacademy.org

It has great videos to explain a lot of basic concepts. Here is the link that teaches you long division:

Another great basic concept website is purplemath.com (for algebra)
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Manager
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Re: Extremely embarassing, can't do long division on recurring d [#permalink]

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04 Nov 2012, 18:55
Hey hi,
10/99 = 0.101010

Hope it helps.

Posted from my month

bile device
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Re: Extremely embarassing, can't do long division on recurring d [#permalink]

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04 Nov 2012, 21:50
VIPS YOU ARE THE MAN

booya

Director
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Re: Extremely embarassing, can't do long division on recurring d [#permalink]

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04 Nov 2012, 22:12
anon1 wrote:
VIPS YOU ARE THE MAN

booya

here is another trick to avoid such lengthy calculation

if u divide a number N by 9s (k times 9), it always gives the same repeating numbers .(0000) N (0000) N
(0000) depends on how many 9s are there.

eg:
2/9 = 0.222222222....
5/99 = 0.0505050505....
10/99= 0.1010101...
111/999=0.111111111..

and so on..
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Re: Extremely embarassing, can't do long division on recurring d   [#permalink] 04 Nov 2012, 22:12
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