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If q is the sum of all factors of 8184, then what is the

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kevincan
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If q is the sum of all factors of 8184, then what is the [#permalink] If q is the sum of all factors of 8184, then what is the   16 Sep 2006, 02:58
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If q is the sum of all factors of 8184, then what is the units digit of q?

(A) 0 (B) 1 (C) 4 (D) 7 (E) none of these



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Re: If q is the sum of all factors of 8184, then what is the [#permalink] If q is the sum of all factors of 8184, then what is the   16 Sep 2006, 03:09
Its A. Thanks to Cicerone :-D
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Re: If q is the sum of all factors of 8184, then what is the [#permalink] If q is the sum of all factors of 8184, then what is the   16 Sep 2006, 03:37
How could this be done without Cicerone's formula, (which is very nice, by the way)?
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Re: If q is the sum of all factors of 8184, then what is the [#permalink] If q is the sum of all factors of 8184, then what is the   16 Sep 2006, 08:35
kevincan wrote:
How could this be done without Cicerone's formula, (which is very nice, by the way)?


I am sorry, I can't find Ciceone's formula. Can someone help?
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Re: If q is the sum of all factors of 8184, then what is the [#permalink] If q is the sum of all factors of 8184, then what is the   16 Sep 2006, 08:42
https://www.gmatclub.com/phpbb/viewtopic.php?t=35249
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Re: If q is the sum of all factors of 8184, then what is the [#permalink] If q is the sum of all factors of 8184, then what is the   16 Sep 2006, 08:44
kevincan wrote:
How could this be done without Cicerone's formula, (which is very nice, by the way)?


This is the way it was sujjested..

8184 = 2^3*3^1*11^1*31^1

= (2^4)-1/(2-1) * (3^2)-1/(3-1)* (11^2)-1/(11-1) * (31^2)-1/31-1

= 15*4*some number*...

unit's digit is 0
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Re: If q is the sum of all factors of 8184, then what is the [#permalink] If q is the sum of all factors of 8184, then what is the   Updated on: 25 Sep 2008, 01:08
I am happy that people r using the formula given by me to answer these questions. I am sure that formulae like these will help us to save time in the exam,

keep rocking folks,

Regards,

Originally posted by cicerone on 17 Sep 2006, 05:02.
Last edited by cicerone on 25 Sep 2008, 01:08, edited 1 time in total.
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Re: If q is the sum of all factors of 8184, then what is the [#permalink] If q is the sum of all factors of 8184, then what is the   17 Sep 2006, 06:20
I get 1 or 7?

Factors of 8184 = 2^3 * 3^1 * 11^1 * 31^1

So either 2+3+11+31 = 47 So units digit is 7

OR

2+2+2+3+11+31 = 51 So units digit 1
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Re: If q is the sum of all factors of 8184, then what is the [#permalink] If q is the sum of all factors of 8184, then what is the   17 Sep 2006, 06:27
cicerone wrote:
I am happy that people r using the formula given by me to answer these questions. I am sure that formulae like these will help us to save time in the exam,

keep rocking folks,

Regards,


sure cicerone...it would definetely save a huge chunk of time
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Re: If q is the sum of all factors of 8184, then what is the [#permalink] If q is the sum of all factors of 8184, then what is the   17 Sep 2006, 06:34
AHHHHH, I've seen the light.

I read as sum of smallest factors, not ALL factors. D'oh!
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Re: If q is the sum of all factors of 8184, then what is the [#permalink] If q is the sum of all factors of 8184, then what is the   17 Sep 2006, 06:38
kevincan wrote:
If q is the sum of all factors of 8184, then what is the units digit of q?

(A) 0 (B) 1 (C) 4 (D) 7 (E) none of these


The factors are 31*11*3*2^3

If we take only fatcors that are not repetitive then it is 7.

If we can take all the 3 2's in 2^3 the it is 1
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Re: If q is the sum of all factors of 8184, then what is the [#permalink] If q is the sum of all factors of 8184, then what is the   17 Sep 2006, 06:44
trivikram, I think I fell into this trap. It asks for the sum of ALL of the factors so 8184, 4092.......1

I think!
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Re: If q is the sum of all factors of 8184, then what is the [#permalink] If q is the sum of all factors of 8184, then what is the   17 Sep 2006, 06:55
Thanks to Kevin for giving such wonderful questions



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Re: If q is the sum of all factors of 8184, then what is the [#permalink]
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