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If n is an integer, what is the units digit of x?

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If n is an integer, what is the units digit of x? [#permalink] New post 30 Jun 2012, 07:00
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If n is an integer, what is the units digit of x?

(1) x = (25^2)/(10^n)

(2) n^2 = 1
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Re: If n is an integer, what is the units digit of x? [#permalink] New post 30 Jun 2012, 07:07
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If n is an integer, what is the units digit of x?

(1) x = (25^2)/(10^n). If n=0 then x=\frac{25^2}{10^0}=625 and the units digit of x is 5 but if n=-1 then x=\frac{25^2}{10^{-1}}=6250 and the units digit of x is 0. Not sufficient.

(2) n^2 = 1 --> n=1 or n=-1. Not sufficient as no info about x.

(1)+(2) If n=1 then x=\frac{25^2}{10^1}=62.5 and the units digit of x is 2 but if n=-1 then x=\frac{25^2}{10^{-1}}=6250 and the units digit of x is 0. Not sufficient.

Answer: E.
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Re: If n is an integer, what is the units digit of x? [#permalink] New post 24 Jun 2013, 02:17
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Re: If n is an integer, what is the units digit of x? [#permalink] New post 24 Jun 2013, 08:31
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Question: Its a value question, we need to know the units place of x, so irrespective of the no if we can get the same units place always, this should be fine.

(1) x = (25^2)/(10^n)

n is an integer, can be positive/negative and even/odd anything.
With any little slight change in value of n the units place digit will change => Not sufficient

(2) n^2 =1

Well n's units place must be always 1, but what about the relation b/w n and x? we still dont know anything about x => Not sufficient

Both combined. (1) + (2)

take n= -1 and n=1
again without any calculation we can see that we will get x=6250 and 62.5 respectively => Not sufficient

Ans=>E
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Re: If n is an integer, what is the units digit of x? [#permalink] New post 26 Aug 2014, 22:47
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Re: If n is an integer, what is the units digit of x?   [#permalink] 26 Aug 2014, 22:47
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