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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 10 Jun 2011, 23:47
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Can someone please explain in detail?

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.
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Re: If n is a positive integer, what is the tens digit of n ? [#permalink] New post 11 Jun 2011, 00:12
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siddhans wrote:
Can someone please explain in detail?

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.


Its A for me ;
st1. 10n = 6.
Look at it in this way,. for example the number 56; 5 in tens place and 6 in units,
multiply 56 by 10 we get 560 ; Now 5 took hundredth place and 6 tenths place,
So we can conclude that when we multiply a number by 10, the orginal designated places( units/tens/hundreds) shifts to the left and takes the next higher place.

so in statement 1. we know hundred digit of 10n = 6
hence we know that the number is 6 X X and thus the original number is X 6 X .
Sufficient

St.2
tens digit on n +1 = 7
suppose the number n is 69
n+1 = 70 = tens digit is 7 , tens digit of n is 6;
suppose n = 70; n+1 = 71
both n and n+1 have tens digits as 7. hence insufficient.

Hope this helps
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Re: If n is a positive integer, what is the tens digit of n ? [#permalink] New post 11 Jun 2011, 00:46
sudhir18n wrote:
siddhans wrote:
Can someone please explain in detail?

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.


Its A for me ;
st1. 10n = 6.
Look at it in this way,. for example the number 56; 5 in tens place and 6 in units,
multiply 56 by 10 we get 560 ; Now 5 took hundredth place and 6 tenths place,
So we can conclude that when we multiply a number by 10, the orginal designated places( units/tens/hundreds) shifts to the left and takes the next higher place.

so in statement 1. we know hundred digit of 10n = 6
hence we know that the number is 6 X X and thus the original number is X 6 X .
Sufficient

St.2
tens digit on n +1 = 7
suppose the number n is 69
n+1 = 70 = tens digit is 7 , tens digit of n is 6;
suppose n = 70; n+1 = 71
both n and n+1 have tens digits as 7. hence insufficient.

Hope this helps


Okay, What does 10n mean here...? 10 multiplied by a number ? and this number is single digit?
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Re: If n is a positive integer, what is the tens digit of n ? [#permalink] New post 11 Jun 2011, 01:15
It cant be a single digit integer because the question asks you for tenths place...
10n = 10 *multiplied* to the number 'n'
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Re: If n is a positive integer, what is the tens digit of n ? [#permalink] New post 11 Jun 2011, 01:51
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1. 10 multiplied by n (n has to be a two digit number)
Once you multiply any number by 10, all the digits get a 'promotion'. So A is suff.

2. The tens digit of n+1 is 7..it can be if n equals 69 or 66..not suff..

Ans A.
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Re: If n is a positive integer, what is the tens digit of n ? [#permalink] New post 11 Jun 2011, 02:03
siddhans wrote:
Can someone please explain in detail?

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.


Whenever a number is multiplied by 10, its digits will shift one to the left

12345 --> 4 is at tens place
x10 123450 --> 4 is at hundreds place
x100 1234500 --> 4 is at thousands place
x1000 12345000 --> 4 is at ten thousands place
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Re: If n is a positive integer, what is the tens digit of n ? [#permalink] New post 08 Nov 2011, 11:29
One of the ways of solving this is coming up with possible numbers
(1)when hundredths digit of 10n is 6 all number for n will have 6 in tenths place 61,365, etc. So sufficient
(2)n can be 69, 70, 71 etc where n+1 will have 7 in its tenths place. So Insufficient

Ans: A
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Re: If n is a positive integer, what is the tens digit of n ? [#permalink] New post 05 Dec 2011, 21:26
say n =XY
statement 1: 10*XY= XY0, where X is the tens digit of XY. Since, XY0= 6Y0, the tens digit of n =6. Sufficient
Statement 2: say XY = 69. XY+1= 70 or XY=70, XY+1=71. Multiple possibilities. Not Sufficient.
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Re: If n is a positive integer, what is the tens digit of n ? [#permalink] New post 05 Dec 2011, 22:40
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Its A for me ;
(1) The hundreds digit of 10n is 6.

say no is 10a+b
where 10's digit is a and unit digit is 6
so 10n = 100a+10b

here hundreds digit is 6 which is a (my tenths digit)


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

say the number n is 23
n+1 = 24 = tens digit is 2 ,
suppose n = 29; n+1 = 30
here ten's digit is 3
hence insufficient.
Re: If n is a positive integer, what is the tens digit of n ?   [#permalink] 05 Dec 2011, 22:40
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