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If a two-digit positive integer has its digits reversed, the

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If a two-digit positive integer has its digits reversed, the [#permalink] New post 14 Apr 2007, 16:54
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If a two-digit positive integer has its digits reversed, the resulting integer differs from the original by 27. By how much do the two digits differ?

(A) 3
(B) 4
(C) 5
(D) 6
(E) 7
[Reveal] Spoiler: OA

Last edited by Bunuel on 12 Oct 2012, 09:22, edited 1 time in total.
Edited the question.
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 [#permalink] New post 14 Apr 2007, 18:33
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A?

Let x be the tenth digit and y be the units digit.

Then, the original number is 10x+y and the reversed number is 10y+x.

The difference between the two is 27. (reversed - original)

Thus, (10y+x)-(10x+y)=27
solve the above eq.
10y+x-10x-y=27
9y-9x=27
9(y-x)=27
y-x=3

Thus the two digits differ by 3.

:)
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 [#permalink] New post 15 Apr 2007, 14:16
salr15 wrote:
ricokevin wrote:
A?

Let x be the tenth digit and y be the units digit.

Then, the original number is 10x+y and the reversed number is 10y+x.

The difference between the two is 27. (reversed - original)

Thus, (10y+x)-(10x+y)=27
solve the above eq.
10y+x-10x-y=27
9y-9x=27
9(y-x)=27
y-x=3

Thus the two digits differ by 3.

:)


how did you get 10x + y?


34 = (3 x 10) + 4
If xy = 34 then this explains it.
HTH
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 [#permalink] New post 15 Apr 2007, 15:25
techjanson wrote:
salr15 wrote:
ricokevin wrote:
A?

Let x be the tenth digit and y be the units digit.

Then, the original number is 10x+y and the reversed number is 10y+x.

The difference between the two is 27. (reversed - original)

Thus, (10y+x)-(10x+y)=27
solve the above eq.
10y+x-10x-y=27
9y-9x=27
9(y-x)=27
y-x=3

Thus the two digits differ by 3.

:)


how did you get 10x + y?


34 = (3 x 10) + 4
If xy = 34 then this explains it.
HTH


Great thanks! :oops:
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Re: If a two-digit positive integer has its digits reversed, the [#permalink] New post 12 Oct 2012, 08:32
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This is a tricky number properties question. Note that you can use two variables a and b to represent each of the digits.

In terms of expressing them in values - the total value would be (10a + b).

For example, for a number 37, a = 3 and b=7..then the expression 10a+b = 30 + 7 = 37.

Please refer to the video explanation here:
http://www.gmatpill.com/gmat-practice-t ... stion/2397


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Re: If a two-digit positive integer has its digits reversed, the [#permalink] New post 08 Jan 2014, 20:10
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Re: If a two-digit positive integer has its digits reversed, the [#permalink] New post 15 Feb 2015, 09:42
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Re: If a two-digit positive integer has its digits reversed, the [#permalink] New post 15 Feb 2015, 13:41
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Hi All,

The "math" behind this question is such that there are several different numbers that "fit" the given "restrictions"; in that way, we can use a bit of "brute force" to quickly come up with the answer.

We're told that a two-digit positive integer will differ from its "reverse" by 27.

I'm going to 'play' with this math a bit.....

IF we use....
12 and 21 then the difference is 21-12 = 9 This is NOT a match
13 and 31 then the difference is 31-13 = 18 This is NOT a match. Notice how the difference increases by 9 though!!!!!
14 and 41 then the difference is 41-14 = 27 This IS a match.

The question asks for the difference in the two digits involved. Using these values, the answer is 4-1 = 3

Final Answer:
[Reveal] Spoiler:
A


I mentioned at the beginning that there were several numbers that "fit" what this question was asking for. They are 14 and 41, 25 and 52, 36 and 63, 47 and 74, 58 and 85, 69 and 96.

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Re: If a two-digit positive integer has its digits reversed, the   [#permalink] 15 Feb 2015, 13:41
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