If n is a positive integer, what is the units digit of n? : GMAT Data Sufficiency (DS)
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# If n is a positive integer, what is the units digit of n?

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If n is a positive integer, what is the units digit of n? [#permalink]

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15 Jun 2013, 22:14
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If n is a positive integer, what is the units digit of n?

(1) the units digit of $$(n+4)^2$$ is 4
(2) the units digit of $$(n+3)^2$$ is 1

[Reveal] Spoiler:
Any other alternative solution
[Reveal] Spoiler: OA

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Last edited by Bunuel on 15 Jun 2013, 23:10, edited 1 time in total.
Edited the question.
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Re: if n is a positive integer, what is the units digit of n? [#permalink]

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15 Jun 2013, 22:18
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From statement 1 we get 2 values for n 4,8

$$(4+4)^2$$ = 4

$$(8+4)^2$$ = 4

From staement 2 we get 6,8

$$(6+3)^2$$ =1

$$(8+3)^2$$= 1

so combined from 4,8 and 6,8

we get 8
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Re: if n is a positive integer, what is the units digit of n? [#permalink]

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15 Jun 2013, 22:27
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if n is a positive integer, what is the units digit of n?

1) the units digit of $$(n+4)^2$$ is 4
2) the units digit of $$(n+3)^2$$ is 1

Given that alone they are not sufficient, combining them we get that:
because $$(n+4)^2$$ has a 4 as unit digit, $$n+4$$ or is 8 or is a two digit integer ending with a 2
because $$(n+3)^2$$ has a 1 as unit digit, $$n+3$$ or is 9 or is a two digit integer ending with a 1

Because the question asks for the unit digit of n, we can conclude that n will have a 8 as unit digit:
X8+4=K2
X8+3=K1
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Re: If n is a positive integer, what is the units digit of n? [#permalink]

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15 Jun 2013, 23:13
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Re: If n is a positive integer, what is the units digit of n? [#permalink]

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26 Nov 2014, 09:57
Hello from the GMAT Club BumpBot!

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Re: If n is a positive integer, what is the units digit of n? [#permalink]

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02 Jan 2015, 02:38
Statement #1 ) : the unit digit of (n+4 ) ^ 2 is 4 : we know that the unit digit of 8^2 is 4 and also the unit digit of 12^2 . so n+4 could be 8 and 12

so n+4 = 8 and here n =4 OR n+4= 12 and Here n=8 so Two different integer and two different result . so Data # 1 Is insufficient.

Statement#2) : the unit digit of (n+3)^2 is 1 : we know that 9^2 has 1 in its unit digit and also 11^2 has 1 unit digit so n+3 = 9 OR 11 and n could be 6 OR 8 this Data

has 2 possible value and is ruled out too....

Combined info : we get 8 from 2 info in common so sufficient ... Answer is C
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Re: If n is a positive integer, what is the units digit of n? [#permalink]

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03 Apr 2016, 09:29
Hello from the GMAT Club BumpBot!

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Re: If n is a positive integer, what is the units digit of n?   [#permalink] 03 Apr 2016, 09:29
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