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If n is a positive integer, what is the tens digit of n ?

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If n is a positive integer, what is the tens digit of n ? [#permalink] New post 18 Dec 2004, 16:39
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Question Stats:

63% (01:47) correct 38% (01:16) wrong based on 60 sessions
If n is a positive integer, what is the tens digit of n ?

(1) The hundreds digit of 10n is 6.
(2) The tens digit of n + 1 is 7.

OPEN DISCUSSION OF THIS QUESTION IS HERE: if-n-is-a-positive-integer-what-is-the-tens-digit-of-n-144725.html
[Reveal] Spoiler: OA

Last edited by Bunuel on 22 May 2014, 12:07, edited 1 time in total.
Added the OA.
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 [#permalink] New post 19 Dec 2004, 09:13
Looks like the Official Answer is A,

can someone explain the logic ?
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 [#permalink] New post 19 Dec 2004, 11:46
Quote:
Looks like the Official Answer is A,

can someone explain the logic ?


1) hundreth place of 10n is 6, so n is a number between 60 and 69 (inclusive).
so the tenth place of n is 6.

2) The tens digit of n+1 is 7 so N can be 69 to 78, so tenth place of n is either 6 or 7.

Hence A alone is sufficient.
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Re: If n is a positive integer, what is the tens digit of n ? [#permalink] New post 22 May 2014, 12:01
mbassmbass04 wrote:
If n is a positive integer, what is the tens digit of n ?

(1) The hundreds digit of 10n is 6

(2) The tens digit of n+1 is 7



I thought the answer was E. I must be not understanding the question?

(1) 10n hundreds digit is 6... but if n is 66 then 66x10=660 and tens digit is indeed 6. However if n is 60, 60x10=600 and tens digit is 0. What's going on? Why is the answer A?

Thanks.
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Re: If n is a positive integer, what is the tens digit of n ? [#permalink] New post 22 May 2014, 12:12
Expert's post
bytatia wrote:
mbassmbass04 wrote:
If n is a positive integer, what is the tens digit of n ?

(1) The hundreds digit of 10n is 6

(2) The tens digit of n+1 is 7



I thought the answer was E. I must be not understanding the question?

(1) 10n hundreds digit is 6... but if n is 66 then 66x10=660 and tens digit is indeed 6. However if n is 60, 60x10=600 and tens digit is 0. What's going on? Why is the answer A?

Thanks.


The tens digit of both 66 and 60 is 6.

If n is a positive integer, what is the tens digit of n ?

(1) The hundreds digit of 10n is 6. This implies that the tens digit of n is 6 (the hundreds digit of 10n is the same as the tens digit of n). Sufficient.

(2) The tens digit of n + 1 is 7. If n=70, then the tens digit of n is 7, but if n=69, then the tens digit of n is 6. Not sufficient.

Answer: A.

Units digits, exponents, remainders problems collection.

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OPEN DISCUSSION OF THIS QUESTION IS HERE: if-n-is-a-positive-integer-what-is-the-tens-digit-of-n-144725.html
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Re: If n is a positive integer, what is the tens digit of n ?   [#permalink] 22 May 2014, 12:12
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