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Starting with 1, positive integers are written one after the

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devilmirror
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Starting with 1, positive integers are written one after the [#permalink] New post   10 Feb 2007, 12:33
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Starting with 1, positive integers are written one after the other. What is the 40,000th digit that will be written?

A. 4
B. 2
C. 1
D. 0
E. 3



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Re: Starting with 1, positive integers are written one after the [#permalink] New post   10 Feb 2007, 17:29
I CANT UNDERSTAND THE QUESTION , ARE U SURE OF THE WORDING??

OR IS IT ME :lol:
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Re: Starting with 1, positive integers are written one after the [#permalink] New post   10 Feb 2007, 17:32
Do you mean if you to write very large number like this:

1234567901234567890.... to 40,000 in length, what would the 40,000th digit be???

Wouldn't it be 0? Or that would be too easy.
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Re: Starting with 1, positive integers are written one after the [#permalink] New post   10 Feb 2007, 18:55
yezz wrote:
I CANT UNDERSTAND THE QUESTION , ARE U SURE OF THE WORDING??

OR IS IT ME :lol:


Here is the sample.

1 then 2 then 3 then 4

123456789 10 11 12 13 14 15 16 17 18 19... keep writing and what is number in the 40,000th digit 8-)
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Re: Starting with 1, positive integers are written one after the [#permalink] New post   12 Feb 2007, 11:32
this is probably an 800 level question, i cant imagine anyone solving this in under 2 minutes
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Re: Starting with 1, positive integers are written one after the [#permalink] New post   12 Feb 2007, 12:09
the answer would be 1.... however i agree that this is not a GMAT question....

here is the trick:
there are 9 1-digit numbers
there are 90 2-digit numbers
there are 900 3-digit numbers
and 9000 4-digit numbers
writing them all gives us 38889 digits.
so the 38890th digit is 1 of the number 10000, the first 5 digit number.
from here on, for the next 10000 numbers (or 50000 digits), each 5th digit would be 1. so 1 is the 38890th digit and 38895th digit etc... and also the 40000th digit.
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Re: Starting with 1, positive integers are written one after the [#permalink] New post   12 Feb 2007, 12:12
devilmirror wrote:
Starting with 1, positive integers are written one after the other. What is the 40,000th digit that will be written?

A. 4
B. 2
C. 1
D. 0
E. 3


1-9 -9 digits total
10-99 -180 digits total ( 2 for each of the 90 two-digit numbers)
100-999 - 2700 digits total (3 for each of the 900 3-digit numbers)

1000-9999 - 36,000 digits total (......)

Clearly, the number containing the 40,000th digit will be a five digit number

Up to 999, we have written 38889 digits
Since 40,000-38,889= 1,111 and 1,111/5 =222 with a remainder of 1,

So, the 40,000th digit is the first digit in 10,222 i.e. 1
A tedious solution- has anybody got another?
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Re: Starting with 1, positive integers are written one after the [#permalink] New post   12 Feb 2007, 17:31
hobbit wrote:
the answer would be 1.... however i agree that this is not a GMAT question....

here is the trick:
there are 9 1-digit numbers
there are 90 2-digit numbers
there are 900 3-digit numbers
and 9000 4-digit numbers
writing them all gives us 38889 digits.
so the 38890th digit is 1 of the number 10000, the first 5 digit number.
from here on, for the next 10000 numbers (or 50000 digits), each 5th digit would be 1. so 1 is the 38890th digit and 38895th digit etc... and also the 40000th digit.


you rule...........amazing solution hobbit :-D
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Re: Starting with 1, positive integers are written one after the [#permalink] New post   12 Feb 2007, 20:56
they would never give this on the GMAT's would they?



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Re: Starting with 1, positive integers are written one after the [#permalink]
12 Feb 2007, 20:56
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